I actually like Sanji because he reminds me of myself.
I am sure that Sanji sometimes felt jelous of Zoro and he probably reminded his father, Judge, words, when like Roronoa wanted to persue his dream and went against Mihawk or when happened the "nothing happened".
Of course Sanji doesn't totally want to be like Zoro, for example he's for sure happy to not be as stupid as marimo.
Sanji wants to be loved and to be a a good support to his crew, I think he possibly thought so many times to actually be a failure as Judge said, I am sure that the cook didn't love himself so many times because of his lack of power, because he couldn't protect his friends, I think he has fought so many times "why am I not strong enough to end this and that?"
That's why he left the crew, he didn't want to be a burden for his friends, that's why he played the bad guy role, he hoped that like he wouldn't have been a burden anymore for someone else.
But he isn't a burden, his mother protected him, his mother protected the "failure" Sanji, and he's not actually a failure, his kindness is the best part of him and reason of his strength, because he's actually really strong.
Because of him not loving himself he pushes his ego and acts in that way with women, he was also jelous of Jinbe when he was hugged, when he apperead to escort Luffy and so he pushed his ego by saying he was the one doing that.
Because of Judge, because of all of that, because of him being called a failure, Sanji wants to be the best.
I am sure that Sanji really admires Zoro for his determination and strength and, at the same time, wants to prove that he's better than him.
At the end, I think that Sanji should start to love himself and his kindness, just like his mother loved him and his way of be.