mammalogy vs zoology

mammalogy and zoology both are nouns.

Word	Noun	Adjective	Verb	Adverb
mammalogy	Yes	No	No	No
zoology	Yes	No	No	No

As nouns, zoology is a hypernym of mammalogy; that is, zoology is a word with a broader meaning than mammalogy:

Other hypernyms of mammalogy include zoological science.

mammalogy (noun)	zoology (noun)
the branch of zoology that studies mammals	the branch of biology that studies animals
	all the animal life in a particular region or period