In WordPress admin -> WooCommerce -> Settings -> Products -> Display(tab)
Find the Product Images section. You can change the image size and select whether to hard crop or not.
After that, use this plugin https://wordpress.org/plugins/regenerate-thumbnails/ to regenerate your Product Images.
Please see screenshot. http://prntscr.com/80lfda
You should prepare your images using your own image editor before uploading them as Product Images. The hard cropping options is not “intelligent”, you cannot choose which part of the image to hard crop.
That’s all I can help on this issue.