JoJo is fairly controversial as far as the speed of the characters goes so i’ll equalize it.
Ultimate Kars in travel speed can fly at best below 240 km/H, but he can react to WW2 machine gun easy, can dodge an ultraviolet beam etc. And that was before being ultimate, so he is likely faster after that.
But here we equalize speed.
Strength wise Zoro is likely a lot better, and he can cut 100 meters of stones, steel doors etc. So Zoro can obviously hurt Kars.
Kars can regen and his regen is good. But I don't know if he can regen being cut in two or if his brain/head is cut.
But Kars is extremely smart (400 IQ) and now has hamon, and his hamon is 1.000.000 better/stronger than Joseph one (who is already good).
And with his hamon everything can become a weapon. Hamon is quite versatile. Kars power with animals and controling his cells into everything is great.
Kars can likely still produce blades from everywhere and those light blades with hamons will be powerful.
But Zoro haki and durability will protect him from a lot of things.
I don't know haha Kars is difficult to gauge right, and even if the fighter against him is more powerful he can lose.
Zoro can win the fight quickly if he goes all out, but the more the fight will going the more Kars will bring bullshit tactics and will understand Zoro way to fight.