I know this is a really old question, but I was googling for a way to do the same and found an extension called Per Tab Zoom that can make CTRL +Scroll Wheel to zoom tabs independently of each other.

When you close a tab, its zoom setting is forgotten.

You can customize a few shortcuts to perform the kind of zoom you want. "Per tab" zoom is forgotten when the tab is closed and "per domain" zoom is remembered for all pages in that domain.