I was tempted to stick with Zoro >= Sanji, but Oda has knocked out the > for me with one choice. Oda has made several narrative decisions, but the strongest one is, framing them as the wings of the Pirate King. Note he didn’t say “Left” arm, and the “right arm”/”Number 2 and 3”, “Number 3” framing only comes from without the crew. Note that in Vivre Cards, both Sanji and Zoro are the only ones with “he’s like a vice-captain”, “he’s like a military advisor” framing.
Pre-amble aside, the concept of “wings” implies equality in itself. It is metaphorical, while a right arm can be stronger than a left arm, wings are perfectly symmetrical. A bird cannot fly with uneven and unequal wings, nor can it ever contemplate to even soar anymore than a man can sprint with one leg weaker than the other.
The visual and pairing has been pushed several times in the Wano Arc alone — despite — and I stress — despite Zoro having impressive feats shown off on the rooftop which I acknowledge as a fan of the entire crew.
Is it reaching to Zoro = Sanji when the story basically says that? Is it delusional to now interpret the words on the page according to what they say?
Sanji’s framing in this picture is odd here, but if you remember the caption as “The wings” take flight, then look at it this way, both Zoro and Sanji’s limbs are extended to artificially resemble limbs. After all, Mouton Mallet has never been drawn that way before.
Oda frames Zoro and Sanji here as Luffy’s “wings”, again involving the image with the shape of the panels. As someone pointed out, flip Zoro and you also get continuity with Zoro and Sanji in the same position, their respective limbs forming a pair of wings alongside Luffy.
Absent a direct confrontation, Oda didn’t have to do any of these. Oda could have made Queen’s bounty much lower than King’s, could have said “left arm” of the pirate king, could have pushed Zoro vs King and Zoro vs Queen separately instead of tying them together several times, could’ve done so many things other than what he did. So I have to reach this conclusion, just as I did in Enies Lobby, and before that in Little Garden before that that this is the story he’s trying to tell.