I really don't understand why ppl are that bothered with the fact that Luffy is stronger than Zoro. He is the MC, Zoro's captain and the future king of the pirates. Shit was inevitable from the jump. If this was a manga about some sword quest and Zoro was the MC, that would be one thing but for people to read a pirate manga for 20+ years where majority of the feats, fights and focus were all about Luffy and come to the conclusion that he is weaker than Zoro is just nuts.
Basically the same scenario with Naruto and Sasuke where everyone and their mums swore Sasuke was the MC's equal, look how well that turned out but in this case, Zoro ain't even a rival which is even worse, he is an underling of Luffy which automatically makes him second best. The moment a character officially joins the SH, they automatically become weaker than Luffy. Franky goes from stalemating Luffy to a potential mid diff, Jinbe was swapping hands with Luffy at Fishman Island and now Luffy is so clear, it ain't even funny. Same goes for Yamato which is unfortunate but it is what it is. If Prime WB was to join the SHs right now, he would be second best to no one (Haha bitch, you really thought)