The Monster Trio Dynamic won’t change — and it’s not just because of strength. Simply put, Zoro and Sanji are reflections of Luffy in ways no other crew member is.
The Four Emperor Situation – Big Mom and Kaido
Aside from the Volume 100 Cover, the Monster Trio are also the only characters with Vs. Yonko covers., and the only two who have proactively attacked an Emperor.
Big Mom and Kaido will fall to Supernova Captains, not Zoro and Sanji, but Oda crafted challenges for them that allowed them to blow over an Emperor in their own unique ways.
When Big Mom is introduced, the first thing we are told is that she cannot be easily satisfied. She has a very specific taste in food, she wants it in a specific way or she’ll rampage and murder everything.
When Kaido is introduced, he is invulnerable. You can’t hurt him, spears shatter against his skin. That sort of stuff.
Oda had two Straw Hats, using their unique skills, “cook”, “swordsman”, break the mythology of these two Emperors with ease.
Luffy, the Pirate King, has a chef that can satisfy the unsatisfiable and a swordman that can cut the uncuttable. He’s already got one over two of the four Emperors. And to be clear, Oda also establishes that Sanji is powerful enough to physically repel Big Mom’s attack, but she’s a woman and he is never going to kick her and to be clear, Oda wrote several feats of physical power and speed for Sanji in Whole Cake. Some people insist on arguing with the narrative like it is a court case. Oda’s intention of showing Sanji blitzing Oven or carries like 60 people, a walrus, a 60-ton cake, and a cart on one leg was not to get you to argue “lol cake” or “Oven wasn’t looking at Sanji sneak attacking from the *checks notes* front of his face.” The fact that the people that attack Sanji are Katakuri and his two triplets is not an accident.
Neither of the two defeated the Emperors with their skills, but it was enough that they stunned and staggered them. Because One Piece is Luffy’s show ultimately.