3dzoom will place a small magnifying glass on your product images that - when hovered upon - will magnify that area of the picture. If there appears to be no difference in the magnified image and your regular image, it could be due to your image sizes and settings.
3dzoom will only work if the image is large enough to actually zoom in on. For example, if you upload an image that has large image dimensions at 1200x1200 and the product display is at 500x500, then it will have information to actually zoom in on.
However, if you use an image with large image dimensions at 400x400, then it cannot zoom in since it is physically smaller than the dimensions used for the display.
To ensure your images can be zoomed on, be sure to use images that are larger than the store's product image display settings.