zillion vs gazillion

zillion and gazillion both are nouns.

Word	Noun	Adjective	Verb	Adverb
zillion	Yes	Yes	No	No
gazillion	Yes	No	No	No

As nouns, zillion and gazillion are synonyms defined as:

zillion and gazillion: a very large indefinite number (usually hyperbole)

Other synonyms of zillion include bazillion, billion, jillion, million, trillion.

zillion (noun)	gazillion (noun)
a very large indefinite number (usually hyperbole)	a very large indefinite number (usually hyperbole)

zillion (adjective)	gazillion (adjective)
very large indeterminate number