combat zone vs war zone

combat zone and war zone both are nouns.

Word	Noun	Adjective	Verb	Adverb
combat zone	Yes	No	No	No
war zone	Yes	No	No	No

As nouns, war zone is a hyponym of combat zone; that is, war zone is a word with a more specific, narrower meaning than combat zone:

combat zone: a military area where combat forces operate
war zone: a combat zone where military operations are coordinated (especially a designated area in international waters where the rights of neutrals are not respected by nations at war)

Other hyponyms of combat zone include bridgehead, foothold.

combat zone (noun)	war zone (noun)
a military area where combat forces operate	a combat zone where military operations are coordinated (especially a designated area in international waters where the rights of neutrals are not respected by nations at war)
a city district known for its vice and high crime rate