Wings doesnt' mean anything in terms of strength, like a certain delusional biased fandom would desperately claim. The Wings just refers to volume 73 SBS where Oda stated that both Zoro and Sanji are trustworthy men who cover Luffys's back. Which is, indeed, what they are, nothing more nothing less. Oda could have easily called them rivals or something in that issue, but... he chose to not.
And, funny thing, even if he did (which, again, he chose to not do) being rivals doesn't mean anything.
You can bicker like Lucci vs Jabra, Kaku vs Jabra, King vs Queen, Luffy vs Kidd, Shanks vs Buggy, Mr 1 vs Mr 2: these are gag rivalries where people just don't get along or friendly compete. You can have a rivalry that is not friendly and not based on gag but is still far from making the two rivals close or equals, as one of the two is much stronger than the other, like Kidd vs Apoo, Zoro vs Killer, Luffy vs Koby.
The supposed rivalry between Zoro and Sanji is a mix of the two aforementioned situations.
A completely different thing are properly said rivalries, like Shanks vs Mihawk, Zoro vs Mihawk, Roger vs Garp, Roger vs Whitebeard, Teach vs Luffy. These are serious strength rivalries where people compete for the pinnacle of strength and/or the same important achievement, and if they fight they would draw of the winner would come out after an extreme diff battle.
It's sad that this certain delusional biased fandom nonetheless continues to try to sustain that if you don't get along then that must be you definitely be equals or almost equals, who cares if anything else, feats, portrayal, benchmarks, paths, goals, roles, shows the opposite...
Zoro is showed, stated and implied by multiple sources to be the second strongest in the Strawhats, Luffy's right hand man and the first mate/vice captain for the rest of the crew.
Sanji is not. Why, you think?
Zoro is a Conqueror and an Advanced Conqueror Haki user, like Luffy.
Sanji is not. Why, you think?
Zoro, as the King of Hell (parallel for Rayleigh as the Dark King) and the future WSS who is basically the King of the Swordsmen, is a king on his own, like Luffy.
Sanji is not. Why, you think?
Zoro, like Luffy, is a Worst Generation Supernova, and was put in the top five Supernovas that received greater hype as the strongest pirates who lead the rising new generation.
Sanji is not. Why, you think?
Zoro needs to fulfill a strength oriented dream that requires him to reach and surpass Top Tiers, like Luffy.
Sanji does not. Why, you think?
Zoro is ofter portrayed as close in strength to Luffy. He is directly stated to have similar strength to Luffy and is shown to fight to a draw with the captain a 1 vs 1 fight that lasts for two chapter and has them use their named move and clash with the intent of prove the other who is the strongest between the two. A fight so serious that they don't want it to be interrupted.
Sanji does not. He is never portrayed as close in strength to Luffy. Why, you think?
Zoro always performs better than Sanji against strongest opponents or similar opponents: just compare Zoro vs Fujitora and Zoro vs Kaido and Big Mom to Sanji vs Doflamingo, or Zoro vs Pica to Sanji vs Vergo. Why, you think?
Zoro is the one who fights to protect Luffy from the very strongest enemies, especially when Luffy is defenseless (vs Kuma and vs Kaido are prime examples of this).
Sanji is not. Why, you think?
Zoro has some Advanced Haki, even two on three, Adv CoC and Adv CoA.
Sanji does not have any Advanced Haki. Why, you think?
Zoro is always in the main events and moments alongside with Luffy. Sanji is not. Why, you think?
Zoro: Oda has him being there for the relevation of Blackbeard with the "is not he, is they", has him in chapter 1000 for the great fight between Supernovas and Yonkos, has him being the only one Strawhat who met both Ace and Sabo.
Sanji: Oda has him not there because he is not relevant enough.
Zoro usually fight enemies strongest enemies than Sanji, enemies that are the counterpart in the opposite crew/group, as the second strongests/number twos/first mates/right hand men.
Sanji usually fights weaker enemies than Zoro, and most of times they are the counterpart in the opposite crew/group, as the third strongests/number three/left hand men.
Why, you think?
Zoro most of times fight someone that Sanji can't defeat (in Alabasta Sanji would lose to Mr 1 who Zoro defeated, in Skypiea Sanji would lose to Ohm who Zoro defeated, in Enies Lobby Sanji would lose or have an extreme diff fight with Kaku who Zoro defeated, in Dressrosa Sanji could not defeat Pica who Zoro defeated, in Wano/Onigashima Sanji would lose to King who Zoro defeated).
Sanji never fought someone that Zoro couldn't defeat (on the opposite, Zoro would make a clown of Sanji's opponents; while, as said, Sanji can't defeat most of the enemies that Zoro defeated in the same arc).
Why, you think?
Zoro always has a fight in every arc.
Sanji does not. Why, you think?
Zoro has many more power ups than Sanji. Why, you think?
Zoro: in Logue Town receives stronger swords than the ones he had before, in Alabasta learns how to cut steel (CoA Haki), in Skypiea learns how to do flying slashes, in Enies Lobby learns Ashura, in Thriller Bark receives Shunsui which is a much stronger sword than the one he had before, then in time skip trains under Mihawk, and in Wano/Onigashima receives Enma and unlocks Advanced Conqueror Haki.
Sanji: in Enies Lobby learns Diable Jambe, then in time skip trains under Emporio Ivankov, in WCI receives the Raid Suit and in Wano/Onigashima unlocks the esoskeleton and learns Ifrit Jambe.
Zoro's main iconic power ups are greater than Sanji's main iconic power ups (Ashura >> Diable Jambe and Advanced Conqueror Haki >> Vinsmoke Esoskeleton and Ifrit Jambe). Not to mention Oda having Zoro training with Mihawk... while at the same time Sanji is training with Emporio Ivankov. Why, you think?
Why does Oda keep making Zoro having parallels and sharing powers and things with Luffy while Sanji has zero parallels with Luffy and barely more than zero with Zoro?I mean... the pattern is clear. Like it or not, it's blatant.
And it should mean something...
That should be more relevant than "they bicker lol"
