steward vs zoo keeper

steward and zoo keeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
steward	Yes	No	No	No
zoo keeper	Yes	No	No	No

As nouns, zoo keeper is a hyponym of steward; that is, zoo keeper is a word with a more specific, narrower meaning than steward:

steward (noun)	zoo keeper (noun)
someone who manages property or other affairs for someone else	the chief person responsible for a zoological garden
a union member who is elected to represent fellow workers in negotiating with management
one having charge of buildings or grounds or animals
an attendant on an airplane
the ship's officer who is in charge of provisions and dining arrangements