void vs strike down

void is a noun but strike down is not a noun.

Word	Noun	Adjective	Verb	Adverb
void	Yes	Yes	Yes	No
strike down	No	No	Yes	No

As verbs, strike down is a hypernym of void; that is, strike down is a word with a broader meaning than void:

Other hypernyms of void include cancel.

void (noun)	strike down (noun)
an empty area or space
the state of nonexistence

void (adjective)	strike down (adjective)
containing nothing
lacking any legal or binding force

void (verb)	strike down (verb)
excrete or discharge from the body	cause to fall by or as if by delivering a blow
take away the legal force of or render ineffective	cause to die, especially suddenly
clear (a room, house, place) of occupants or empty or clear (a place or receptacle) of something	declare null and void; make ineffective
declare invalid