Yamato looking like Inuyasha sister.
What Zoro accomplished was completely different than what Kiku did. Zoro permanently scarred Kaido. A feat achieved by only one other person throughout the entire manga, Oden.
Kiku slightly injured Kaido, who quickly healed the injury. Kiku feat was repeated by every other Scabbard plus Luffy, Kid, Killer, and Law.
I always find it funny how some compare Zoro to Kiku when they try to downplay him instead of using any of the other Scabbards.
Zoro hasn't prroved his worth to himself yet because his goal wasn't to scar Kaido. Instead, it is to kill Kaido. That's part of the reason he will return and fight Kaido again.
Kaido has been beaten several times. Oda told us about all his losses when he officially introduced him. He is no stranger to defeat. Defeating Kaido won't be enough to stop him because he will return. Remember, he stated he picked Wano for a reason. Zoro is the only one capable of killing him. Not right now but in the future. Regardless of who Zoro fights next, he will use it to improve his skills/control over enma and CoC.
I believe the only way to kill Kaido is to hit him with an attack powerful enough to kill him in one blow. Anything less won't kill him. It might severely injure him, it might defeat him, but it won't kill him because he will recover. I think that will be achieved by having Zoro combine a large overflowing amount of haki with powerful adv CoC attack.
Flying dragon blaze 2.0 incoming.