Eh, Zoro's reaction was completely different. Kidd is the one who was left confused and didn't even know what he saw. Zoro recognised it as the application of haki that Hyou taught Luffy.
He questioned. He didn't recognize it. Luffy probably told him off-panel that he trained advanced haki with the old man Hyou, but he didn't know what it was before seeing Luffy actually use it and questioning if it's what Luffy told him before
Yeah, Zoro is going to become stronger during the fight. As Zoro's strength matures during this battle, Kaido will recognise him as a "monster samurai" of the calibre of Oden.
The more it's going, the less likely it become. As stated, last chapter, Luffy was the one who was given the burden of Oden's scabbards to save Wano. In this chapter, Oden is among the shadows Kaido sees in Luffy after Kaido thinking Luffy shouldn't match him. All heads towards Luffy being the only one to be able to match him in a 1 on 1 since Oden, who also could have bested Kaido on his own if not for the hostage thing.
Zoro on the other hand at best would participate in weakening Kaido by either opening the old scar or creating a new one, which would show Zoro's
potential comparatively to Oden, but not actually placing him in the same caliber of people who'd match him in a 1 on 1, where Luffy would be portrayed to be