The fact that Mihawk achieved the WSS title is enough proof that he should have Conqueror's Haki just not confirmed yet.
When it comes to Zoro's training well. Did Rayleigh tell Luffy how he can apply CoC? Yeah, no.
There is a huge problem with Zoro and CoC reveal.
Dude is the first or one of the first people on WCI to praise Luffy for using CoC and now he wonders what the fuck Kaido talks about.