Well, Zoro, all cross the first half of One Piece, was consistent in one thing. All if fights were about him pushing himself to new limits, overcoming his physical restrictions. Might seem similar to Luffy, but it differs in one extremely crucial thing. Zoro fights with technique, whereas Luffy fights with heart. Of course, there are instances where his initial technique wasn't at par, so he had to develop new techniques, such as his fight against Daz Bones, in Alabasta, but, still, his heart was about pushing his physical limitations to fully back up his technique, working past injuries and weakness. Yet, if an opponent presented himself with much superior technique, Zoro would sacrifice himself and humbly accept defeat, but wouldn't be able to come out victorious. Zoro vs Mihawk, Zoro vs Arlong, Zoro vs Kuma. That's Zoro's way. He is extremely powerful and skillful, but understands defeat and, while he would sacrifice himself for his piers, he can't go past his technique, that's his limitation.
Luffy is different, he doesn't fight with technique, he fights with heart, with gut. All of Luffy's major opponents far surpassed him in skill, and Luffy's win wasn't him surpassing their skill (Like Zoro's fights are), they were him being more resilient, brave and driven than any of his opponents. He holds his drive and ambition in his fists, and goes all out. It is not a matter of who fights better, it is a matter of who wants more. Because Luffy doesn't fight, he brawls, so you don't have to surpass his skill, you have to surpass his drive. It is the basis of Haki, I believe, since it is just a physical demonstration of spirit, and hey, it's extremely in character, he is the rubberman, you punch him and he just comes back up ten fold. I truly believe his greatest defeat, at the hands of Kuma, wasn't because Kuma surpassed his ambition, it was rather that Kuma broke Luffy by showing him his friends disappearing, and making him confront with his lack of skill, and, thus, breaking his ambition/spirit.
So, back on topic. There is no way Zoro would be able to defeat Lucci, even if one could argue that, in terms of raw power, Zoro and Luffy are pretty much the same. What Luffy achieved against Lucci was inhumane, even for Zoro. I'm sure Zoro would give one hell of a show, and would then be defeated heroically, but wouldn't be able to defeat him. Luffy would most likely defeat Kaku, at great expense, though, 1. Because he would find his Giraffe form hilarious and distract himself from the fight and 2. because swords and sharp attacks are a really great weakness of Luffy.
