Luffy collapsed and almost died from a bite from Hody. No big deal. He later goes on to fight YC levels.
Zoro takes a scythe Killer, who was stronger than before, because he was distracted from an opponent he dropped his guard against and instead of dropping his stops killer from pulling the scythe out of his body by just flexing his muscles. He doesn't fall during the battle. He trains to grow stronger but he can't fight King because he is going to faint during battle, something that has never happen before.