If people really want to be psycho fanboys, sanji demonstrated advanced swordsmanship before Zoro did, back in enies lobby when he cut Wanze's noodles off him without touching his skin. Zoro couldn't do precision stuff like that until he was cutting the royal family's shackles off in fishman island.
A swordsman can cut through steel if he wishes, but the same sword can be stopped from cutting even paper, according to the skill of the swordsman, according to the guy who taught Zoro. And Sanji did it first with kitchen knives. Lol