I mean it doesn't really matter:
It should be pretty obvious to any rational fan that Killer got stomped by Zoro.
Objectives: Killer's objective was to fulfill Orochi's orders so that his crew will be kept alive. So he needed to kill the girl.
Zoro's objective was a to save two random strangers he met.
Who completed their objective: obviously Zoro.
The fight itself:
1. Gyukimaru interferred with the fight, which caused Zoro to get hit.
2. Killer got one shotted by Zoro afterwards.
3. Zoro falls unconcious from the hit that was caused by Gyukimaru's interference. However, he completes his objective in saving Hyori and laughing girl
You can argue full strength or not all you want, but two facts remain.
Zoro one shoted Killer and he completed his objective. He's undisputed winner of the fight.
And who cares if Zoro fainted or not. He already completely his objective. People forget that One piece has a storyline and isn't entirely focused on 1 v 1 fighting. Characters often have inconsistent feats based on the storyline. For instance, we saw Crocodile get beaten by beginning of series luffy and then later do impressive things to top tiers during Marineford.
Now, if we want to get a little subjective, if Killer was on Zoro's level, shouldn't we expect him to at least last longer. He was in a better situation. Zoro has to guard the girl at all times. And finally, he landed a blow on Zoro. But he couldn't stop Zoro from one shotting him. Whats to say in a fair 1 v 1 fight, Zoro couldn't do the same. And Killer hasn't shown the ability to land a blow without help on Zoro.