petting zoo vs accumulation

petting zoo and accumulation both are nouns.

Word	Noun	Adjective	Verb	Adverb
petting zoo	Yes	No	No	No
accumulation	Yes	No	No	No

As nouns, accumulation is a hypernym of petting zoo; that is, accumulation is a word with a broader meaning than petting zoo:

Other hypernyms of petting zoo include aggregation, assemblage, collection.

petting zoo (noun)	accumulation (noun)
a collection of docile animals for children to pet and feed	the act of accumulating
	several things grouped together or considered as a whole
	(finance) profits that are not paid out as dividends but are added to the capital base of the corporation
	an increase by natural growth or addition