Before our vacation, a client send me an email asking about his problem. Which is about the product images frame that is too small for his product images that longer from the frame.
Do some experiment in my local host, and finally i could solved the problem.
Heres how to enlarge JQZoom size in prestashop themes.
First, go to your prestashop/css/jqzoom.css file. change the width and height values from the code below: