Remember when Buggy owned Zoro when they first met? He almost killed him! And back then, Zoro wasn't even able to touch him. Yea, I miss those days where Buggy was higer ranked and more dangerous to the crew. Even Luffy struggled with him and maybe wouldn't have won without Nami's help.
But now, after TS. If Buggy fought with Zoro again; who will win? Keep in mind that if Zoro doesn't have Haki his swords wont be helpful. And also, Buggy might have gotten stronger, and he will be fully equipped(with swords, knives, bombs and everything)
If you want my opinon, I wish Buggy would win :/ although it's a bit far fetched.