[Zordon's Legacy Exposed]

Zedd likely left for what he thought wouldn't be for very long. He had to protect his Dark Galaxy from some outright threat. Be that Vile or someone else. Rita was just supposed to maintain Zedd's Territory in the Earth Sector. But she escalated an offensive against Zordon and his army. Pretty much for her own personal gain and risked the wrath of Zedd if she failed. Succeeding would have allowed her to overthrow Zedd or at least rise in the hierarchy of the UAE.

Once Zordon and Rita had their stalemate ( Rita trapped in the Dumpster and Zordon the timewarp) Zedd had no reason to return to the tarran sector. Since it was no longer an attractive area by that point. And more importantly Zordon was thought to be dead. Rita was most likely assumed dead as well, as the good guys wouldn't advertised where she was trapped. But in any case Zedd didn't care about her any longer either. As he could boast his forces finished off Zordon without worrying about Rita being around to take the credit.

Once Rita escaped and Zordon was outed as being alive. There was much more incentive for Zedd to see Zordon get taking out. Also Vile took over the Dark Galaxy by the end of Season 1. Zedd had to rebuild his empire. And what better way would it be for him to finally revive Rita and be the one to really take out Zordon. Zedd would have been extremely mad at Rita for her failures and wouldn't want her around. He would also know that she would stab him in the back at the first opportunity.