These instructions are for are section-based themes: Turbo 2.0+, Parallax 3.0+, Retina 4.0+, Mobilia 5.0+, and Responsive 6.0+. If you are on an older/pre-sectioned version, please update your theme.
You can disable the image zoom on your product images within the theme settings.
Head to Customize > Theme settings > Product grid. There are several options for the Product Gallery. One of these options is "Hover to Zoom", which will zoom on the featured product image as you hover over it, or tap and hold on mobile.
This option can be changed to "Fade" or "Slide" to disable the zoom feature.