We recommend the Featured Image Zoom plugin for adding an image zoom feature to your WordPress site. This plugin allows you to easily add a [zoom] shortcode to your pages, posts, or custom post types that have a featured image, and when users hover over the image, it will be magnified while the image viewport remains constrained to the original image dimensions.
For mobile and touch devices, the image can also be zoomed using a pinch and zoom action, making it accessible for all users. The plugin offers several optional shortcode parameters, such as the ability to specify the image size for the unzoomed and zoomed images, as well as the level of zoom. This ensures that the magnified image looks great and provides the desired level of detail.
With over 1,000 active installations and a 4.5-star rating, the Featured Image Zoom plugin is a reliable and well-received solution for adding an intuitive image zoom feature to your WordPress site. The plugin has also had issues resolved in the last 2 months, indicating that the developer is actively maintaining and improving the plugin.