So? It's not like Luffy's base stat's stayed the same either and just because Zoro has new moves it doesn't mean them attacks are stronger than Luffy's attacks. What we seen from Luffy and Zoro vs Aqua Laguna both of them let out an equally strong attack Zoro was using 3 swords and Luffy was in base mode. It seems your basing who would win purely on strength of attacks it takes more than just powerful moves to win a fight especially in a fight that involves both Luffy and Zoro. Of course I don't think Luffy would win easily but I think ultimately if the two went at it Luffy would come out the victor. Gear 2nd only really increases Luffy's speed and attack power but I believe Luffy has the necessary strength and speed in his base form to keep up with Zoro and damage him.
They are comparable in speed, so the winner will be the one with the strongest attacks. Yes Luffy's base stats upgraded i don't deny that, but like i've said, his strongest one hit attack remained bazooka when Zoro had a variant of the oni giri that Luffy matched(embima oni giri), as well as rashomon, shishisonson and his flying slashes that he developed later, so while their base stats likely improved at the same rate, Zoro had stronger attacks. Like i've said, Luffy
needed gear 3 attacks to break steel in enies lobby something Alabasta Zoro could do with Shishisonson, so let alone later. His attacks were simply stronger
Not to mention that in terms of endurance, Zoro outclasses Luffy(thriller bark prove that) and he was tanking hits from Oz who has much stronger attack power than gear3 Luffy. The damage output shows the endurance, will and strength Zoro had and it won't be easy for base Luffy to put him down when he could take on much stronger attacks and continuing fighting as if he was healthy