Hi,
Yes, it is working, but you need large product pictures to see the real effect of zoom.
If the thumbnail is 90x90 and the large product picture is 100x100, of course the zooming will only enlarge the picture from 90x90 to 100x100, which is almost not-noticable.
Product (original) pictures should be larger than 900x900 for the best user-experience. Because zoom effect doesn't virtually scale up the pictures, but it uses the original (large) picture as reference inside the zooming area.
Regards.