It makes very little sense for Zoro and Luffy to train their haki to an advanced level to take on folks like Ancient Zoans and then have Sanji with zero training and beat a calamity. Sanji didn’t get a single hit on King, he was busy not trying to die
1st:
Where did Zoro used or trained for Advanced CoA? All he did was try not to get sucked out by Enma and get it under controll.
2nd:
When have you Sanji seen train? Never. Does this mean he never trains? When have you Luffy ever see train on the Ship? Yet he was always stronger than Zoro who we often see train.
3rd:
Lol, get your feelings under controll. Sanji was protecting a child in his arms while clashing with King. Sanji was never the one attacking, but blocking and King didn't manage to land a hit. Only after Sanji ignored him and was talking to Momo, King could prepare his attack. Read the manga...
Zoro never showed anything that would put him on YC level and he is struggling against much weaker foes and even getting hurt by literal fodders, but he is magicaly YC level and above...aight