It will be Nothing Happened 2.0. A character defining moment for Roronoa once more. This is the most desperate situation Zoro has found himself in since the Time-skip began.
We're about to witness the greatest acts of a Samurai: Protecting your liege with all your might. Luffy is Zoro's lord, the one he's forsaken his honor for, the one he's tirelessly trained for during the 2 years, and this arc is heavily steeped in displaying loyalty, and inner strength coming from it. The Scabbards lament how they could not protect Oden. Yasu spurred them on to be Oden's and Wano's guardians. Zoro will be just that for Wano and Luffy.
What will differ from Thriller Bark is that Luffy will witness Zoro's actions. He's already started to with Zoro repeatedly rescuing him. Another way is that Zoro lacked the strength and support to hold off Kuma, and only survived because Kuma honored his devotion. This time, though, Linlin and Kaido are resigned to killing the rookies no matter what. Zoro has the strength and support to fend them, at least for 10 minutes.
Many things can occur during these 10 minutes. Zoro unleashing Asura for the first time in over a decade, displaying Conqueror's haki. Kaido recognizing him as a powerful Samurai. Asura is due to Luffy already being compared to an eastern deity, with Zoro looking the same in Asura. Zoro's aura has been a plot point as early as Act 1, being compared to a confirmed Conqueror's haki user like Oden, and even Brook mentioning King's haki.
And of course, Kaido starting to notice Zoro more and more as the battle progresses. Actions speak louder than words, and Zoro's actions are beginning to ring loudly in Kaido's ears. He has been commenting and wondering about Zoro like he has the Scabbards. His evaluation of the latter was a resounding failure.
What will be his final mark on Zoro, I wonder?