Zoro and Sanji being Luffy’s wings is very fitting because they represent different sides of him. I think that’s also why their dreams both parallel Luffy’s in particular ways. Zoro’s is a dream of ambition. Sanji’s is a dream of passion while Luffy’s is both. The two only Straw Hats who have had their dreams directly compared to Luffy’s.
Zoro’s strength comes mostly from his drive to be the best. And innate natural belief in himself. Sanji’s strength comes from the passion and emotion that he has(everything his family thought made him weak). Luffy’s comes from both. Zoro and Sanji are two parts of Luffy’s coin from my interpretation. That’s why they have all these parallels and conflicts.
Another thing I appreciate is how Zoro and Sanji have inverse character arcs . Zoro was born with an innate insurmountable level of self worth. He strives to be the best for the sake of being the best. He already wanted to be the greatest swordsman before he even met Kuina and always felt like it was something he was destined to do for no paticular reason. Nobody told him he needed to be the best or that he was special. He just believes in his greatness and constantly exudes that at a very young age.
He believes strongly in fate which allows him to bet on himself in situations like when he picked out his cursed blade and had the mentality that if he dies he was only meant to make it this far. When he met Luffy his dream was above all even his own life and he told Luffy he would kill him if he ever got in the way of that. Despite this ego and intense self importance he ended up willing to cast it aside for the sake of his captain and his crew because they are worth his life and dream. I see him asking Mihawk to train him as a continuation of this because he is not just wanting to be the worlds greatest swordsman for the pride of the position, he needs to be the strongest to support Luffy and the crew. His crew and his captain are worth that sacrifice. That’s the gift Luffy gave him.
Sanji on the other hand was born into a family that told him he was special and destined for greatness though at his heart he was only ever truly interested in his passions. Then shortly after as a child the concept of his greatness was ripped away from him because of who he was. Sanji’s upbringing with Germa had serious damage to his sense of self worth and created an intense self sacrificial nature in him. His family put him through physical, psychological and emotional abuse consistently to drill in the idea that he was worthless at a very tender age.
We see his self sacrificial nature throughout the story in the way he puts his crews well-being above his own and his willingness to die to protect the Baratie for Zeff’s sake. He has been very willing to sacrifice his life for others dreams because he was taught he and his dreams have no worth. The Black Maria was the most important character development payoff moment for Sanji because it showed after Whole Cake Island he was able to allow people he cared about and that he trusts to risk themselves in order to save him for the first time. Because he is worth it. That is the gift that Luffy gave him.