black out vs zonk out

black out and zonk out both are verbs.

Word	Noun	Adjective	Verb	Adverb
black out	No	No	Yes	No
zonk out	No	No	Yes	No

As verbs, black out and zonk out are synonyms defined as:

black out and zonk out: lose consciousness due to a sudden trauma, for example

Other synonyms of black out include pass out.

black out (verb)	zonk out (verb)
lose consciousness due to a sudden trauma, for example	fall asleep fast, as when one is extremely tired
suppress by censorship as for political reasons	lose consciousness due to a sudden trauma, for example
darken completely