And that's the thing, he acknowledged luffy as captain and then the bond he made throughout the series and got developed to the the point where he is doing his dream For Luffy's sake before for himself. I don't think I need to explain how it has been given more details than that of other members.So what? That doesn't change anything. They still weren't familiar with each other or bonded to each other. Zoro two seconds after he became Luffy's subordinate is still the same person 2 hours before he became Luffy's subordinate. There's no development or character change there.
So? Franky is still further along Zoro in this category because Franky developed from someone who was actively attempting to kill Luffy to someone who would die for Luffy. Franky went from hating Luffy to being devoted to him, while Zoro went from indifferent to devoted. Franky has come further, regardless of status as Luffy's subordinate.
Neither of them. Zoro took Luffy's pain, showing he'd die for Luffy. That's been the greatest display of Zoro's devotion to Luffy. Not only did Oda make it clear every single Strawhat would have done the same thing, but just before that every Strawhat chose death over giving Luffy up. There hasn't been any special characterization of Zoro's loyalty. There WAS when he took Luffy's pain, but that was made no longer special when it was stated any of them would have done the same thing.
But was it given as much details as zoro's development? Nope.
Any other strawhat who would've smacked luffy for doing something that would harm his own pride? No. That counts too. Any other who has pride as big as zoro but still bowed to another man? No. Another example I gave above, the line that zoro said to usopp about luffy. Usopp leaving crew and other little instances can by found on this topic alone. This is what it means to show us different aspects of one's character. And these are things which only a person with zoro's mindset could've done. And if he inspired these qualities in others too after he did it then, well, I would give others credit too but obviously more to zoro.