i wasn't sure about if a zone is an object, therefore the question dubilcate rule is for objects.
The codex defines objects, saying that Creatures, Conjurations, Enchantment, and Equipment all become objects AFTER they are cast, and the Mage is also an object. So, you are correct that Zones are not objects. Thus, why I stated the rule as "You can't have more than one copy of an object attached to the same
thing." It might not be a very precise term, but here I was using thing to mean anything that might have objects attached to it.
The specific place for Conjurations is on page 16 of the English Rulebook v3, where it says "A zone may never have multiple conjurations with the same name attached to it" and a separate sentence that says "An object may never have multiple conjurations with the same name attached to it." These mirror similar rules to be found in the Enchantment and Equipment section, thus why I lump them all into a universal rule.
Technically, there is no such section for Creatures, which is why my universal rule is a little dangerous as a generalization. However, since there are no Creatures that currently attach to anything, I feel safe with my universal rule. Just have to remain vigilant for any new expansions which may force me to reevaluate it.