It's do able - but there are cons
You can place an image into a "Pan and Zoom" Overlay - make that full screen and stick it in a Multistate object with a tumbnail, then place an invisible button over the thumbnail
This is a work around, and if you place the invisible button on the thumbnail, it will still be active when "Pan and Zoom" is initiated so you'll have to have a play regarding user experience!
Hope this helps
First state empty frame so that whaterever is on the page is visible
Second state the enlarged image
Button with Go to Next State action will hide/show the full screen image.
Make sure that it is a PDF folio and you will be able to zoom the full screen image as well
It wouldn't be 100% full-screen, but you might also save your image as a PDF and link to it locally using the 'HTMLResources' method. When you tap your button (or hyperlink) the PDF viewer will pop open with your image.