The ongoing Brooklyn-based trial of Joaquin “El Chapo” Guzman has revealed that the Mexican drug lord trafficked an alleged 440,000-plus pounds of cocaine, bought a zoo and built his own miniature train on which to ride around his Guadalajara property. But perhaps the most surprising move by his Sinaloa Cartel? Hiring the world’s oldest drug mule.

Leo Sharp was an 85-year-old decorated World War II veteran when, in 2009, he transported his first shipment for the Sinaloans, albeit of cash, not narcotics.

But, as chronicled in the new Clint Eastwood movie “The Mule,” in theaters Friday, he soon emerged as the cartel’s most dependable, and highly prolific, mover of cocaine.

“I don’t think state troopers and highway patrolmen were suspicious of an elderly man driving cross-country,” Sharp’s lawyer, Darryl Goldberg, told The Post.

Over the course of 2010 alone, Sharp delivered more than a ton of white powder — enough for some 7.25 million people to each snort a line. But it all came crashing down when the 87-year-old great-grandfather was found transporting 104 bricks of ­cocaine in the trunk of his Lincoln pickup.

As an officer popped the lock and opened the hatch, Sharp reportedly had just three words: “Oh, my God.”

Stolid and resolute, Sharp possessed the kind of man’s-man persona that apparently attracted the actor who made his bones as Dirty Harry. “Something about Leo resonated,” said screenwriter Nick Schenk. “Maybe [Eastwood] wanted to do the flip side of Walt Kowalski” — the embittered World War II vet he played in “Gran Torino.” Added Schenk: “I think of Leo as being charming, ­upbeat and social.”

Sharp was born in 1924 and raised in Michigan, where at age 11 he began working alongside his alcoholic father in the local coal mines.

According to court documents, Sharp’s dad “squandered his money,” leaving a teenage Leo to briefly skip out on high school and toil full time in the mines. After returning to school and graduating in the early 1940s, Sharp entered the US Army and served as an infantryman during World War II. Fighting in Italy, he survived the Battle of Mount Battaglia while his captain and many fellow soldiers perished. In acknowledgment of his bravery and heroism, Sharp received a Bronze Star.

Post-war, he settled in Michigan City, Ind., a touristy spot bordering Lake Michigan. Over the next several decades, Sharp married and split up twice, had two children and adopted two more. Years earlier he owned a taxi service and a home-building company, and was a partner in a local airline.

But by the mid 1990s, Sharp had emerged as a master cultivator of daylilies, creating eye-catching flower hybrids at his Brookwood Gardens floral company, situated on a 46-acre farm near Michigan City. Gardener Nikki Schmith was quoted in The New York Times describing the elderly grower as “a stud” in his newfound career.

Sharp cultivated some 180 official varieties of lilies, but his business reportedly experienced a downturn when customers began buying seeds via the Internet and he did not adapt to the digital world.

Goldberg said that one of Sharp’s employees likely brought him to the Sinaloa Cartel’s attention. “It makes sense that a farmhand of Mexican descent introduced him [to the cartel],” Goldberg said.

It didn’t hurt that Sharp supposedly had previous experience in the field of smuggling: During the early 2000s, it has been alleged by the federal government in court, he drove marijuana and cocaine east from the West Coast for an unknown entity.

In the cocaine trade, octogenarian Sharp immediately stood out among fellow smugglers. He was ridiculed for his advanced age — according to court records, Sharp’s handlers made fun of his failing memory. But he was also given the nickname El Tata, Spanish for The Grandfather, and received preferential treatment. Sharp sometimes got confused while trying to locate stash houses, so cartel members would meet him at highway exits and escort him, and the drugs, the rest of the way. A typical route involved picking up cargo in Arizona and driving it to nondescript warehouses in Detroit.

Sharp proved to be an excellent mule. “He was successful because he was unlikely,” said Goldberg. It’s estimated Sharp earned more than $1 million for himself, spending a sizable chunk on a flower farm near Orlando, Fla., where he hoped to recharge his lily business.

But according to court transcripts, when the old man told cartel bosses he wanted to get out of the drug trade, they responded by putting a gun to his head. “They threatened [Sharp] and said they would kill his family,” Goldberg told the United States District Court for the Eastern District of Michigan.

So he continued on, by then age 87. While drug bosses can be heard on wiretaps discussing how to deal with El Tata’s ambivalence toward making pickups and deliveries — “Brainwash him,” one supervisor advised — Sharp had his own rationale for what he did.

During a 2013 interview with Chicago reporter Chuck Goudie, Sharp equated the coca plant used to produce the drugs with his daylilies: “All God’s plants that cheer people up are created for a purpose,” he said. “To take people’s minds and make them feel good.”

On the afternoon of Oct. 21, 2011, Sharp was driving Interstate 94 to Detroit in a truck full of drugs when Michigan Trooper Craig Ziecina pulled him over near Ann Arbor. The officer said it was for tailgating and improper lane use. In reality, said Goldberg, DEA agents had been stealthily monitoring Sharp. Working with Ziecina, they brought in a drug-sniffing dog that “alerted” as soon as he neared the Lincoln — providing legal reason to search the car.

Despite being busted with 229 pounds of cocaine, Sharp did not seem to immediately recognize the severity of his situation. “When I met Leo, soon after his arrest, he smiled,” said Ray Richards, the attorney who represented him early on. “He looked at me and said, ‘I’m in trouble, huh? I lived my whole life without issues. Now I have gone afoul of the law.’”

Sharp acknowledged as much to the courts where he was charged with conspiracy and cocaine possession with intent to distribute. Still, he did not rat out his co-conspirators. “Old school, literally and figuratively, he accepted responsibility and was not going to take anyone down with him,” said Richards. Sharp ultimately pleaded guilty to drug conspiracy charges.

Although Goldberg argued in court that his client showed signs of dementia, Sharp ended up sentenced to three years at Federal Medical Center, Rochester, a prison in Minnesota. As part of his plea deal, he agreed to give his Florida property and $500,000 to the government.

However, suffering from an undisclosed terminal illness, Sharp served just one year of his sentence. It was anticipated that he would die soon after his release, but he lived in freedom for nearly 16 months, passing away on Dec. 12, 2016.

Despite his criminal record, Sharp held on to his legacy as a military hero. He is buried at Honolulu’s National Cemetery of the Pacific, known as the Punch Bowl, alongside veterans of World Wars I and II and the Korean and Vietnam wars. Befitting his love of flowers, the setting is lush with foliage.