war zone vs combat area

war zone and combat area both are nouns.

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

As nouns, combat area is a hypernym of war zone; that is, combat area is a word with a broader meaning than war zone:

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)
combat area: a military area where combat forces operate

Other hypernyms of war zone include combat zone.

war zone (noun)	combat area (noun)
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 military area where combat forces operate