Zoro didn't fall from Killer but from hunger/stomach problems. There is a difference. That was why Zoro's stomach made the same noise Luffy's stomach made when he passed out. That was after all fighting was over meaning he wasn't going to allow his stomach to interfere with the battles.
It doesn't matter how you look at it Killer didn't knock Zoro out.
Zoro was nerfed too. He only has 2 swords and didn't use any name attack until after he grabbed the scythe. The fact he put the scythe to better us than Killer shows us the difference between them. Zoro could have ended the battle sooner if he would have used a name attack earlier.
Oda used that battle to hype Zoro and Killer. Killer hype came from fighting even with Zoro, while using 2 swords not two sword style, in CQC for a while with scythes. Zoro hype came from fighting and beating Killer and Fox at the same time with 2 swords, quickly adapting the scythe to his fighting style and blitz and oneshot Killer with the scythe with a name attack. Later on informing us the fight results would have been the same even if Killer had his punisher blades.
I believe the same thing will happen with King and it's the reason Zoro fought Kaido and Big Mom on the roof first. Oda wanted to hype up Zoro with them and give us a better understanding of his strength. He will now use those 2 to hype up each other. King hype will come from fighting Zoro and not being easily defeated. It wouldn't be a low difficult battle. Zoro hype will come from improving his CoC during the battle and beating King without being pushed to his highest level.