I've added 5 pictures in Product Photos.
I've added 5 pictures in Product Zoom Images for the respective Product Photos.
The photos in Product Photos are sized 97x150.
The photos in Product Zoom Images are sized 389x600.
In Product Details module, the lightbox (settings turned on) shows the 97x150-sized image instead of the 389x600 image.
It seems as though the images I'm uploading in the Product Zoom Images area are resized down to smaller than 97x150 even (at least as the previews show in the Product Zoom Images tab).
Attached is a screenshot of what happens. Next post will have all the settings details for you.