Translation guide
The most common and natural way to say 'zoo' in Japanese is 動物園 (どうぶつえん). This is the standard word used in almost all contexts.
The speaker wants to refer to a zoo as a location or institution.
This is the standard, neutral word for 'zoo'. It can be used in both spoken and written Japanese, and is appropriate in all registers.
週末に家族で動物園に行った。
We went to the zoo with the family on the weekend.
この動物園にはパンダがいます。
This zoo has pandas.
A direct loanword from English, occasionally used in names of specific zoos or in very casual, trendy contexts. It is not the standard way to say 'zoo' and may sound unnatural if used generically.
Using ズー instead of 動物園 can sound like you are trying to use English in Japanese. It is not recommended for general use.
新しいズーがオープンしたらしいよ。
I heard a new zoo opened.