If it is a service animal, trained, yes. Untrained animals may get scared or disturb animals there.
No.
It's a zoo it has wild animals that would react badly to something else being in their territory so you're not supposed to bring outside animals and because it could bring pathogens or sicknesses that the other animals aren't able to fight off. Service animals can because they are usually vaccinated against everything because it's kind of required care for the animal
Yes.
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