Can't believe I had to battle in the wrong order. I thought it was going to be Zoro versus King battle prior to fighting Kaido. It should be Zoro versus Kaido, King and then back to Kaido.
Luffy need all the supernovas help on the dome because he need a help against 2 Yonko and he wasn't ready to face A Yonko alone.
Zoro's main role during that battle was protect Luffy while he grew stronger. Zoro was better prepared for the battle and stronger than Luffy up until the end of this chapter. He always showing incredible speed and reflexes, the strongest defense we've seen he stopped hakai one of the strongest attacks, an incredible attack power when he injured Kaido with an attack that will leave a scar. Zoro achieve that while severely injured.
Since Luffy is know ready to fight Kaido by himself it's time for Zoro to grew stronger. For Zoro to grow stronger during battle he first needed to be pushed to his limit.
This is going to be sweet. Zoro will beat king before returning to help Luffy against Kaido and finish him off.