Holy COPIUM here when it comes to King lol.
Some of you guys really thought that Luffy's armament would damage King when Zoro's armament couldn't.
Anyway, it's just stuff that we know. Conveniently, Zoro forgetting that King could be damaged when he went KoH, Oda doing everything he can to extend this arc by not having Luffy and Zoro use advanced conquerors haki.