It wouldn't have killed Kaido but it would have at least created a permanent scar equal to his Asura mode attack. I believe that for four seasons.
1 - Big Mom was very concerned about the attack and even told Kaido to not underestimate him. There's no reason for her to be concerned if that attack wouldn't have left a permanent scar.
2 - the attack not only completely cut the horn off at that distance but it had so much power it shook the entire Island.
3 - Zoro was in very poor condition when he performed his Asura mode attack. Yes, we have seen Zorro in bad shape before but the manga has never went out the way to show us the severity of Zoro's injuries. He was also running low on haki. All of that would have affected the strength of his attack.
4 - advance CoC is not needed to injure Kaido. The more strength and haki placed into an attack the stronger it becomes.