slumber vs log Z's

slumber is a noun but log Z's is not a noun.

Word	Noun	Adjective	Verb	Adverb
slumber	Yes	No	Yes	No
log Z's	No	No	Yes	No

As verbs, slumber and log Z's are synonyms defined as:

Other synonyms of slumber include catch some Z's, kip, sleep.

slumber (noun)	log Z's (noun)
a dormant or quiescent state
a natural and periodic state of rest during which consciousness of the world is suspended

slumber (verb)	log Z's (verb)
be asleep	be asleep