Without plot shield, Zoro wins extreme difficulty. Luffy already said his armament isn't great against cuting attacks and Zoro has one of the best cuting arsenal seen in this manga so far, and his attacks are really fast. His 1080 Pound Cannon was so fast Pica didn't even have time to switch inside his golem rock. Not to mention Zoro can implement armament in his flying slashes to increase their power
He could dodge Pica's attacks despite the environment advantage without even looking at him and talking to his crewmates, could see Hody's drop bullets even before it changed form, so it implies great reflexive speed and observation(just like Luffy). While Luffy dominates him in striking speed, he possess faster attacker with his flying slashes and his 1080 Pound cannon easily matched if not bested Luffy's Grizzly magnum(which is his strongest bazooka attack in G3) in terms of scale