Yes your proposed behavior sounds reasonable as well and probably better fits "zoom in/out toggle".

What I think would be more useful than zoom in/out toggle however, is to have different zoom levels and then a zoom out and zoom in button that zooms in/out to the next zoom level.
So:
press zoom in -> zoomed in
press zoom out -> normal
press zoom out -> zoomed out
press zoom out -> zoomed out
press zoom in -> normal

Because I think its more natural if the action is always the same and reflects what you want to do (zoom in/out) independent of the current zoom state (which you should not have to recall in the heat of battle).