malacology vs zoology

malacology and zoology both are nouns.

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

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

malacology: the branch of zoology that studies the structure and behavior of mollusks
zoology: the branch of biology that studies animals

Other hypernyms of malacology include zoological science.

malacology (noun)	zoology (noun)
the branch of zoology that studies the structure and behavior of mollusks	the branch of biology that studies animals
	all the animal life in a particular region or period