YITH WooCommerce Watermark

YITH WooCommerce Watermark lets you apply a logo or a watermark to all your product images. The Zoom Magnifier plugin uses a different image size, so the  Watermark plugin will add this specific image size in the available image sizes.

zoom and watermark

In order to make the two plugins work together, you will only have to activate the premium version of both of them.

For more information on how to set up the watermark plugin, take a look at the full documentation here.