If your theme supports image zoom on products and you are wanting to disable it, this is usually done in the theme settings.
- Go to Online Store » Themes » Customize theme
- If you are using a new theme such as Debut that supports sections, browse to a product in the theme editor
- Under Sections, click on Product pages (or similar) and look for the image zoom setting
- If your theme does not support sections, you may simply need to find the "product settings" option in the theme settings and look for the setting relating to image zoom