Yes, there fucking is. There is the fact that not even Roger or Whitebeard accomplished what you think Zoro will accomplish.
Give me a single evidence that either of them EVER TRIED to kill Kaido.
Kaido HIMSELF says that Oden is SOFT just like Roger and WB were.
WB isn't someone who goes around killing people.
Don't bring up God Valley, that was 40 years ago, Kaido is younger than BM, he was a teenager at best back then, Roger isn't gonna fight such a small fry
Zoro isn’t going to come out of the fight better than Luffy if he helps in fighting Kaido. That’s arguably the biggest obstacle keeping Zoro from killing Kaido
-There are 2 Yonkos in this arc
-Luffy and Zoro can defeat Kaido together with Zoro having the finishing blow.