Add the [zoom] shortcode to a page, post or custom post-type entry. The featured image at the ‘large’ size will then be displayed on the page. When you move the cursor over the image, the image zooms to show the ‘full’ size featured image cropped within the boundary of the image.
The Featured Image Zoom plugin can be downloaded from the WordPress.org plugins directory at http://wordpress.org/plugins/featured-image-zoom/.
This plugin was built to enable specific functionality for a customer project, and is based around the elevatezoom script. There are no options in the initial version, but some options to enable additional features may be added in a later version.
This plugin is supported on WordPress.org at the featured image zoom support forum.