Hi, Kovid.
I saw a few posts asking zooming images by more simple way then present in Calibre for now and decided to give my +1 vote in this challenge

Please, could it be implemented by any way you like but not so complicated: Right click -> move cursor to View image option -> Left click -> View image window.
E.g.:
1. like it was in Edge browser before Epub support was removed - hover over desired image (cursor changes to magnifier) -> Left click -> Window with enlarged image
2. like in Picviewer CE+
https://greasyfork.org/en/scripts/24204-picviewer-ce
And is it possible to memorize View image window's position and size even after exit Calibre?
Best regards, Igor.