I want to be clear we are talking about the same thing here... What is the mechanical process that is used to decide when combat is resolved? If you say zeroing out of hit points then it would mean no NPC or monster can surrender, run away, etc.
There are several depending upon the objective of the combat and the fiction surrounding it:
* Ablate Team Monster HP to 0.
* Force the Enemy Leader to Surrender (mechanically).
* Get to location x on the battlemat with y squares between you and Team Monster or before round n.
* Protect NPC Standard and Minion so they survive 4 waves of enemies.
* Survive 6 rounds until reinforcements arrive and take your spot on the wall so you can withdraw to the motte.
* Survive the enemy while you complete the Ritual/Skill Challenge to Close the Gate or Open the Gate and go through.
* Fight off your possessed friend's attacks while you exorcise him from the demon within him (Adjure Skill Challenge).
Plenty, plenty more. There are plenty of transparent win/loss cons to establish for combat outside of "get enemy HP to 0."