Zetta thought Rhiow had communicated with Ildy et al. during her meeting on Agrestic. But honestly, that wouldn't have changed his actions anyway; he saw a chance and took it.

Zetta is selling himself and the Council (or, if specifically pressed, Kang and Rhiow) to Yavek as a group willing to kiss butt to save the universe, and fed up with but unable to control the majority of the crew and make them fall in line. He's trying to convince Yavek to give the Council greater power over the ship, and to let the Council pretend to be with the rebellion in order to ferret out the leaders and submit them to justice. (He's also managed to cite his own legitimate complaints about the clones taking one for the team on Galilee, and in the process had discovered that the disaster on that planet was a large factor in the Daligig coming on board now.) He's also claiming that the rebellion has leaders better-hidden than the obvious people.

Come the fake rebellion he'll be on the Dalgig's side like you wouldn't believe.