kill zone vs killing zone

kill zone and killing zone both are nouns.

Word	Noun	Adjective	Verb	Adverb
kill zone	Yes	No	No	No
killing zone	Yes	No	No	No

As nouns, kill zone and killing zone are synonyms defined as:

kill zone and killing zone: an area where a battle has occurred with many fatalities

kill zone (noun)	killing zone (noun)
an area where a battle has occurred with many fatalities	an area where a battle has occurred with many fatalities