Facts is that Zoro fought an official battle against Killer, a guy of his tier. He won, but he was knocked out as well since he as well had a direct wound from him.
Zoro vs Yonko is a skirmish for the Yonko, not his official vs, he only could do a support role. Hakai lasted for "a moment" and continued like nothing after that. Zoro was saved from it in time. The attack wasn't stopped completely at all, that's why it could continue after that, it was very brief, so let's say Zoro dealt with 1% of it.
A 1% from that attack is not stronger than a direct hit from a YC lvl opponent attack. Yonko are not 100 times stronger than YC and that attack didnt even have Advanced CoC.
Easy maths.
Luffy's example is the same as Luffy vs Satori. Author nerfing his own MC, making him a hype tool so the enemies look strong. Did several times in the manga. Luffy could won battles much earlier in many of the arcs and finishing them earlier as well. He was thrown out like a shit by Pica, he forgot there he had G4 and could fly, because author needs to set up all the other stuff before giving his MC the last moments, the more epic ones.