zizz vs forty winks

zizz and forty winks both are nouns.

Word	Noun	Adjective	Verb	Adverb
zizz	Yes	No	No	No
forty winks	Yes	No	No	No

As nouns, forty winks is a hypernym of zizz; that is, forty winks is a word with a broader meaning than zizz:

Other hypernyms of zizz include catnap, light sleep, nap, short sleep, snooze.

zizz (noun)	forty winks (noun)
a nap	sleeping for a short period of time (usually not in bed)
a buzzing or whizzing sound