
You can access Firefox's zoom function with three keyboard shortcuts Ctrl+
+ Ctrl+
- (Ctrl+mouse wheel) and Ctrl+0 to reset to 100%.
But then there's this great tiny add-on which let's me access the browser's zoom function
exactly the way I wished to:
move the mouse cursor over the icon
mouse wheel zooms
left click resets to 100%
install & more info
here