So the full summary is out.
Big Mom suggests to Kaidou that they attack together and finish all Supernovas in one blow.
Kaidou: "I hope your legs and hip are still good enough, old hag!!"
Big Mom: "Who do you think you are talking to, boy!!"
Big Mom and Kaidou: "Hakai (覇海 Conquering the Sea)!!!"
Haki is more powerful than I expected. It seems to be the ultimate attack of the Yonkou.
They decide to destroy all the Supernova with their full strength and so unleash their most powerful combination attack:
Hakai.
Big Mom and Kaidou use a massive combined attack, they swing their weapons at the same time and send massive wave at the Supernova which is too fast for any of them to dodge. However, Zoro blocks the attack with his swords.
Zoro outreacts the other 4 Supernova and blocks Hakai for a few seconds.
Zoro: "Get out of the way or we will all die!!"
He holds back the attack for long enough to tell the others to dodge (and they do). The attack is so powerful that Zoro affirms that they will all die if they don't dodge (he was determined to lay down his life to hold off the attack).
Big Mom and Kaidou attack destroys part of the island. Law transports Zoro out in time so he survives but is heavily injured. Kid thanks Zoro for managing to slow down the attack even if he managed to do it for 1 second.
Hakai destroys part of the island and eventually overpowers Zoro. Law returns the favour and transports Zoro away before the attack completely destroys him. Zoro nonetheless takes heavy damage.
Luffy immediately jumps again and uses "Gomu Gomu no Red Hawk" at Kaidou, but Kaidou dodges it before Luffy can complete the attack. Luffy smiles.
Luffy: "So you have to dodge it because this can actually hurt you, right?"
Confirmation that Kaido would dodge attacks he thinks can actually do real damage to him.
I'm guessing that like Red Roc, Red Hawk also uses internal destruction COA. Maybe this naming scheme will be how Oda let's us know that internal destruction COA is being used. Alternatively, Kaido has a weakness to fire (Boro Breath did hurt him after all).
Zoro (that is still coughing up blood)
Hakai really did a number on Zoro.
My main update on the full spoilers is that Zoro's endurance is not quite as godly as I thought as he didn't completely tank Hakai. Other than that, Zoro's defensive prowess is still top tier as he could hold back Hakai for a few seconds.
@Kuro Ashi, while the Supernova focused most of their offense on Kaido, they had to contend with the attacks from both Yonkou working together. Before Mama was defeated, she did a number on Kidd and together with Kaido on Zoro (he was still coughing up blood when he neutralised Prometheus).