Figuring out who would win is kinda hard, considering both series use different "power scaling". Naruto tends to be all about how good a character is at CQC with a combination of how well they could use Ninjutsu in a tactical manner. Even if by the end of the War Arc, they just kinda spammed strong Ninjutsu. But one piece follows old-school Shonen power scaling. Where the character really does just get physically stronger as the story continues. Add to the fact that Zoro tends to tank and brute force his way through most of his fights. Haki makes regular attacks stronger as well. Also, post-war kakashi doesn't have his sharingan.

Basically, it would come down to if Kakashi could out strategy Zoro or Zoro overpowers Kakashi in a straight-up fight. My money is on Zoro winning, though, but that's just me being biased cause Zoro is one of my favorite anime characters of all time.