Asus was not on the radar of most US phone buyers until the ZenFone 2 popped up a few years ago with solid specs for a reasonable price, but the ZenFone 3 family hasn't been as prominent. It took Asus ages to roll these devices out in North America, and the pricing was not as generous. However, there are more variants of the ZenFone 3 still trickling out, from the flagship-level "Deluxe Special Edition" to the low-cost "Laser." The ZenFone 3 Zoom is somewhere in the middle with its $329 price tag and mid-range Snapdragon 625 chip.

The ZenFone 3 Zoom has some very impressive aspects, like the massive 5,000mAh battery and a camera with 2.3x optical zoom. At the same time, it is severely disappointing with an old build of Android, slow charging, and non-backlit navigation buttons. The result is a phone I don't hate, but not one I love either.

Specs SoC Snapdragon 625 RAM 3GB Storage 32GB Display 5.5-inch 1080p AMOLED Battery 5,000mAh Camera Dual 12MP with f/1.7 aperture and 2.3x optical zoom, 13MP front camera Software Android 6.0.1 with ZenUI Measurements 154 x 77 x 7.99mm, 170g

The Good Battery life This phone edges out the Moto Z Play for the best battery life I've experienced. It'll last a solid three days on a charge. Camera The optical 2.3x zoom is neat. Build quality The aluminum build makes the phone feel more expensive, and it's slim for having a huge battery.

The Not So Good Navigation buttons The capacitive nav buttons aren't backlit, which is just crazy, Asus. Camera again Low-light performance is not as good as advertised. No OIS on zoom lens. Software Ships with Marshmallow. Asus ZenUI is unattractive and clunky. NFC Doesn't have it. Connectivity No band 12 LTE handicaps the ZenFone 3 Zoom on T-Mobile. Charging Appears to use QC 1.0, which is much slower than current standards. Takes over 3 hours to completely charge the battery.

Design and display

The ZenFone 3 Zoom is one of the better designed devices in the ZenFone 3 family. The chassis is primarily made of anodized aluminum rather than the hardened glass used in many flagship phones, and it's surprisingly slim for having a giant battery. At the top and bottom are plastic caps, which is where you'll find the antennas. These don't detract from the premium feel of the phone, though.

The back is home to a fingerprint sensor, and it's in the right place unlike Samsung's rear-facing sensor. The ZenFone 3 Zoom's sensor is passable, but it's not as fast as phones like the G6 or OnePlus 3T. It's also a bit slower than the Pixel to recognize and unlock. The sensor doesn't produce any vibration when it recognizes a finger, which is unusual. Instead, you only get a vibration when a read fails. Most phones do one when an unlock is successful and two when it fails. I suppose that might draw attention to the somewhat sluggish nature of this sensor.

At the top of the rear panel is the dual camera array, the layout of which gives this device a definite iPhone vibe. The overall rounded shape is pretty reminiscent of the iPhone, too. The bottom edge has a Type-C port, headphone jack, and the single speaker. The audio on this phone is not a selling point, but it's not bad either. I don't like the location, but Asus is hardly the only offender there. The power and volume buttons on the right edge are clicky and don't rattle around.

The bezels on the front are about the same size as the Pixel XL, which is to say they're big. At the bottom are the capacitive navigation buttons. They're responsive and in the correct order, but the icons are not backlit. It's a real flashback to the ZenFone 2. The lack of a backlight makes the buttons extremely difficult to use in a dim environment. That's just plain bad, but it's not the only strange hardware omission. There's also no NFC or support for band 12 LTE (a big deal on T-Mobile). This is obviously not a flagship phone, but these are still features I'd expect.

The display itself is 5.5-inches and 1080p in resolution. It's an AMOLED display, so the blacks are truly black. The display is capable of 500nits of brightness, but it seems awfully reluctant to go there. In almost all light levels, the ZenFone 3 Zoom looks dimmer than other phones.

Colors are always tough on AMOLEDs; some panels have blown out colors, and others look dingy. The ZenFone 3 Zoom's panel is mostly on-target from what I can see. The white balance is slightly warm, but not so much as to be immediately noticeable. Going with 1080p AMOLED at 5.5-inches will save power, and I think it looks good enough. You can tell it's pentile if you look closely, but it's probably a fine trade-off in the pursuit of crazy battery life.

Camera

There are two cameras on the back of the ZenFone 3 Zoom, neither of which physically zooms. Both sensors are 12MP with an f/1.7 aperture, but one has a "regular" lens and the other has a built-in optical zoom of 2.3x. The camera app switches back and forth between these cameras smoothly, so you don't have to choose one or the other like you do with LG's standard and wide-angle cameras.

Below the cameras are the RGB color sensor, flash, and laser autofocus. The laser sensor offers reliable focus, and it's certainly fast enough. Samsung phones are faster, but they do cost a lot more. The focus speed is on par with phones like the LG G6 and OnePlus 3T, but it's better in dim light. The ZenFone 3 Zoom cameras use both optical and electronic stabilization, which I've found to be very reliable but a bit aggressive. Even small movements cause the frame to "float" around in response. This can interfere with framing, but at least you don't get blurry shots. Unfortunately, the zoom lens doesn't have optical stabilization, so you need a steady hand.

Photos taken in bright light are overall very good with accurate exposure and colors. Asus' HDR mode has improved substantial in the last few years. It's still not as good as Google's or Samsung's, but it makes a clear difference. Although, the ZenFone 3 Zoom has a tendency to blow out very bright areas of the frame even with HDR. The white balance is slightly too warm, too. I should also note, greens tend to get a bit "neon" at times.

In poor lighting, the ZenFone Zoom is very much hit or miss. Asus is keen to point out that its cameras can take in more light than others, and it has a raft of metrics to describe this like "8 times more than a phone with a specific 16MP sensor." The photos taken in low light do look brighter than I expected, but a big part of that is the way Asus pumps up the ISO. Even average indoor light pushes the camera to ISO800-1000 and as high as ISO3200. These images are softer than what you get out of phones like the Moto G5 Plus or OnePlus 3. In low light, the ZenFone's ISO goes up to 12,800. Here, you can see what's going on in the frame, but it's quite noisy. The laser autofocus helps make the images somewhat usable by ensuring sure your subject is in focus. I suppose you can count this as a win of sorts.

There are some things in Asus' camera app that I really like, and some I could do without. In the "like" column is the handy one-touch zoom control. You can use multi-touch to zoom if you want, but there's a button in the viewfinder that instantly snaps to the maximum 2.3x optical zoom. That's probably what you want anyway most of the time. There's also a button that flips over to manual mode with sliders for ISO, exposure, and so on. I'm less enamored with the way Asus crammed a bunch of mediocre camera modes into the app. Some of them don't even make sense. For example, depth of field mode aims to fake a shallow DOF image using both cameras. Just like all past attempts to do this on a phone, the resulting photos are a mess. Super HDR? It seems to actually reduce the dynamic range. Just stick to auto or manual mode and you can take some nice photos.

Performance and battery

The Asus ZenFone 3 Zoom is running a Snapdragon 625, which is starting to get long in the tooth. I don't expect we'll see this chip in phones much longer, but it's not necessarily a bad SoC. In fact, some phones like the Moto Z Play have performed admirably with the 625. However, others haven't been optimized very well at all. The ZenFone 3 Zoom falls somewhere in between. It's not completely smooth, but it's more than usable.

Here are some benchmarks to obsess over if that's your thing. More details below.

The ZenFone 3 Zoom is never going to blow you away with its speed, but I don't find myself waiting on the phone to do basic things. Sometimes apps are a bit slow to open, but again, it's not enough to make the phone tedious to use. A lot of the mediocre performance is likely due to the software, which I'll get to shortly. The phone has 3GB of RAM while other phones are offering 4GB or more. Still, this device seems to keep apps in memory for the appropriate amount of time (after disabling the aggressive RAM manager). Gaming on the Snapdragon 625 is okay as long as it's a simpler title. Heavy 3D games will get choppy, though.

Still half the battery left and nearly eight hours of use.

The battery life is where this phone truly shines. As usual, keep in mind that everyone's usage is different. My experience might not exactly match yours. That said, I used the ZenFone 3 Zoom for email, messaging, browsing, taking photos, and a little light gaming. The 5,000mAh cell in the ZenFone 3 Zoom was able to see me through around three full days of moderate use. This is the strongest battery life I've experienced on an Android phone, barely edging out the Moto Z Play.

As long as your phone is charged in the morning, I see no way you could drain the battery in a single day with any normal usage. The ZenFone 3 Zoom should get you 16-17 hours of straight use. Of course, that's not a realistic amount of time for anyone to use a phone continuously. You'll see somewhere on the order of 10-12 hours of screen time over the course of a few days. Again, this is fantastic.

I've never seen it hit 2A.

There's a downside to the battery situation, though. Asus has implemented "BoostMaster fast charging," which the company tells me is rated at a maximum of 5V/2A. That just happens to be the exact Quick Charge 1.0 spec, and it's extremely slow by current standards. It takes more than 3 hours to charge the ZenFone 3 Zoom's 5,000mah battery. I would expect it to take a bit longer than other phones, but this is ridiculous. It puts a damper on my enthusiasm for the ZenFone's stellar battery life.

Software

The software my biggest issue with the Zenfone 3 Zoom, and it's the main reason I have trouble recommending this phone to anyone. It ships with Android 6.0.1 Marshmallow, which is not okay at this point. Nougat has been available for more than six months, and somehow Asus couldn't find the time to get this phone up-to-date before launching it? This makes me worry about this phone's update prospects, but then, Asus has never been great at updates.

Putting up with Marshmallow wouldn't be so bad if it weren't for the terrible Asus ZenUI. It's bloated, awkwardly designed, and packed with features that are both unnecessary and downright detrimental to the experience. Put simply, Asus ZenUI is what TouchWiz would be right now if Samsung hadn't cleaned up its act.

The Asus home screen hasn't evolved since the Lollipop days, so it still packs garish colors, huge icons, and clunky animations. I'm particularly annoyed by the animation when opening a folder—the icons fly into view like the "laser" text animation from old versions of PowerPoint. It takes a full second for the animation to complete before you can press anything. It's the same when you open the home screen settings or open certain menus. This makes the phone feel slower than it is. The only saving grace of the home screen is that you can change the icon pack, but at that point you might as well just use a different launcher. If you're hoping to re-skin the system UI, don't get your hopes up. The Asus theme store is stocked with some ugly things that cost a few bucks each.

The quick settings and main system settings look the same as they did a few years ago. The colors are seemingly random—some icons are blue, others are green, a couple are orange, and a few are a different shade of green. I don't see any appreciable improvements, and there are a few bizarre additions since the last time I used an Asus phone. For instance, Asus is really emphasizing the memory booster and autostart manager. The boost feature is almost par for the course these days. Many OEMs include something like it, but there are half a dozen ways to trigger it on the ZenFone 3 Zoom (settings menu, quick settings, home screen shortcut, overview, and more). You hit the button, and all your apps close. The default settings even kill background apps when the screen is off, which is an even worse idea. This does not make your phone faster and is liable breaks things. Likewise, the autostart manager prevents all installed apps from starting in the background without your intervention.

Luckily, the most annoying memory management features can be turned off. Still, that should not be necessary. At the same time, some features I actually like are disabled and buried in the settings. Case in point, double-tap to wake and swipe gestures that can wake up and launch an app like the camera. These are actually useful, but Asus has them turned off. This entire build of Android feels confused and awkward.

I can only hope that Asus has delayed Nougat this long because it's making a lot of overdue changes. The build of Marshmallow on this phone is miles behind the competition.

Conclusion

The ZenFone 3 Zoom is probably not a phone I would use on a regular basis, but that doesn't mean it's a bad thing. It has several strong points, which might be exactly what you're looking for. It has the best battery life of any Android phone I've used. That's great, but the slow charging really limits how much I can praise the battery life. Three hours to recharge a phone, even with a 5,000mAh battery, is not acceptable in 2017.

The ZenFone 3 Zoom has a mostly aluminum frame with a solid feel, and one I like more than the glass backs on so many other phones. Despite having such a large battery, it's not a behemoth of a phone. Asus did a good job cramming everything in there, although the shape does look quite a bit like the iPhone 7 Plus.

The camera could be a strong selling point for many people; the 2.3x zoom feature gives the ZenFone 3 Zoom an edge over other phones in this price range. The performance in most lighting conditions is at least competent, and sometimes it's excellent. The indoor and low-light shots are not as good as Asus' marketing would lead you to believe, but I've seen worse. The lack of optical stabilization of the zoom camera is a letdown, too.

There are several hardware decisions that I have a hard time understanding. The non-backlit navigation buttons are a significant annoyance—it's hard to know where to press when using this phone in a dark room. The lack of NFC is also baffling at this price point. And no band 12 LTE? I thought we were done worrying about that.

I hesitate to recommend this phone to anyone right now mainly because of the software. The ZenFone 3 Zoom ships with Marshmallow and a pretty atrocious version of ZenUI. The menus, pre-installed apps, and home screen are all clunky and unattractive. Asus also insists on including aggravating RAM management features. You can disable them, but phones should not be killing background tasks out of the box. It doesn't improve performance, and can break apps and running services.

So, the battery life is fantastic and the camera is good, but the slow charging, missing hardware features, and bad software leave me disappointed. If the ZenFone 3 Zoom gets a Nougat update that improves the Asus UI, the ZenFone 3 Zoom could be a solid purchase. Until then, I think you should hold off.