During One Piece’s Wano Arc, we saw both Zoro and Sanji struggle in their fights against King and Queen, respectively. Both Strawhats had to figure out their opponents, as well as some internal issues, before finally overcoming their respective challengers.

Zoro’s main challenge versus King was that he couldn’t figure out when to attack King, nor how to overpower him. While Zoro eventually learned the timing on the former, the latter was solved via his awakening of standard and Advanced Conqueror’s Haki.

Sanji’s main challenge in the Queen fight was more of an internal struggle with himself as his Germa exoskeleton awakened and changed him. While Sanji’s exoskeleton and Ifrit Jambe power-ups are undoubtedly formidable, they’re far from the level of Advanced Conqueror’s Haki.

Realistically speaking, Sanji’s Ifrit Jambe and exoskeleton put him roughly on par with pre-Conqueror’s Haki Zoro. However, Zoro’s awakening of standard and Advanced Conqueror’s Haki have vaulted him into the ranks of the strongest people in the series.

As a result, the gap between Sanji and Zoro (and implicitly, Queen and King) has grown tremendously since Zoro’s awakening. While Sanji is still certainly impressive in his own right and undoubtedly useful in a fight, he’s nowhere near a Conqueror’s Haki Zoro.

Therefore, it’s more likely than not that Sanji would have lost to King if Sanji had fought the Lunarian instead of Zoro.

Sanji’s exoskeleton and Ifrit Jambe likely have him at a level where he can fight any Yonko Commander and have a decent shot at winning. However, having Advanced Conqueror’s Haki puts Zoro in contention for the top ten strongest One Piece characters, a feat which Sanji can’t currently match.

In summation

Due to Zoro having awakened Advanced Conqueror’s Haki against and using it to defeat King, Sanji likely would’ve lost if he and Zoro switched places. The Ifrit Jambe and Sanji’s exoskeleton are invaluable tools that will see heavy use and importance through the series’ end.

Yet the importance of standard and Advanced Conqueror’s Haki cannot be understated. It’s quite literally the most crucial ability in contemporary One Piece and will likely continue to be for a long time.