I don't see any reason the equipment rule has to behave the same way as the zone rule.
The equipment rule seems like it exists because you need to be able to cast a new weapon to replace an old one and send it back to your spellbook. But because you can't do two things at once, the old armor has to go back to the spellbook before the new one can attach (because new can't come before old is removed). That's two separate things that happen: old is removed, then new is attached.
Movement isn't like that., You don't leave your zone then enter a new one, you just move. Leaving an old zone and entering a new one are consequences of that movement, but they're not separate actions.
If there's ever a time where a creature has left it's old zone but not yet entered its new one, I can break the game. Email me to ask how if it's not apparent.