Is there a specific image size, resolution (dpi) or format (jpg, gif, etc.) the photos need to be for effective zoom image? Thanks.
No specific size is required for the zoom images they just need to be bigger than the regular product image in order to show the zoom effect. So depending on what size your normal product images are will drive the size of the zoom image uploaded. For example, if your product image is 400x400 than your zoom image could be anywhere from 800x800 to 1500x1500 depending on how much magnification you want.