Sorry but this has absolutely nothing to do with our Zoom Effect Extension.
We don't provide support if the problem is not created by our templates/extensions.
IF you don't have too many product pictures, you can manually open each product and correct the thumbnail URL's. But this won't work or takes years to do if you have more than thousands product pictures.
You should better create topic on
forum.virtuemart.net to see if there is an easy way to do it.
One option would be; By using PHPMyAdmin, you can correct the thumbnail URLs all in one with a custom SQL query.
Regards.