Regardless of your opinion for Zoro’s role in the Kaido fight, It’s very important for Him to defeat King in this arc and would be a complete disservice to his character to receive any assistance against him. First I want to establish the usual structure of Zoro’s fights:
Zoro fights the enemies #2 1 v 1 and usually they fall under one of these criteria that help him to continually evolve as a combatant:
1. He Seeks out and overcomes the strongest swordsman of the opposing group
2. His opponent provides him an obstacle/material that he must cut
1. He Seeks out and overcomes the strongest swordsman of the opposing group
2. His opponent provides him an obstacle/material that he must cut
I see the term “Pure swordsman” thrown around a lot but Oda clearly views many characters who use other abilities in conjunction with swordsman as suitable obstacles for Zoro to overcome. For instance Kaku (Zoan, Rokushiki), Pica (Swordsman + Stone Fruit), Cabaji (Acrobatics)
Now that we established the Formula, King actually falls under both categories. He is Kaido’s #2, a swordsman confirmed by OP mag 6, and provides something Zoro can learn to cut with his Fire. This will be a battle of pure endurance, Physical strength, Swordsmanship, etc