So the reason zoro will fight kaido is cuz hes strong? Okey yeah seems right
There is endless list of reasons , i will tell you some of those i remember:
1) Kaido is an Azure Dragon and Zoro is the White tiger ( chinese zodiacs )
2) Zoro is the descendant / reincarnation of Ryuma the God of the sword who Killed a Dragon ( gyukimaru referenced it in wano for a reason)
3) Enma has the hinerited the will of Oden to get Kaido's head and liberate Wano
4) Zoro's cape at the start of Wano had a Sun on it ( = Dawn )
5) 9 shadows = 9 sword style
6) Zoro has an ongoing plot line with Kaido
7) Zoro is likely from Wano and Kaido 100 percent killed his daddy
8) Zoro is the only one who's both strong enough to kill kaido and actually Kills people ( Luffy doesn't kill)
9) 9 thousand million references to "Severing Kaido's head" , luffy can't severe people head with a punch
10) btw Killing kaido after Luffy defeats him makes no sense in terms of Zoro's character and honor so it HAS to be a 2 vs 1 with Luffy
11) Wano arc starts with Luffy and Zoro and Ends with Luffy and Zoro
12 ) Zoro and Luffy had parallel plotlines in Wano ( Tama/Toko, Hyogoro/Yasu, Enma/COA, chapter 1010 CoC )
BTW THERE IS EVEN MORE