Hold on. Power Rangers only use their weapons in self defense. Killing is a last resort and not preferred if possible.
Zordon did fight Rita himself, a long time ago (in physical form, sealing her away until her slumber was disturbed.
Zordon can only do so much, being a non-corporeal being (made up of energy).
He knew Rita could be a threat later after defeating her, though he was in a weakened state (converted himself into energy out of self-preservation using the what little magic and strength he had left, creating the morph gadgets too).
Why teenagers though? I dunno, maybe teamwork and stuff like that.
Well movie Zordon was a bit too pushy and pretty wanted forcing a group of teenagers who technically they didnt know each other that well to have them go kill an ancient martial arts warrior. That and forcing them to focus to activate their battle armor which they couldnt since they didnt know each other and they had personal problems.
I dont care if movie Zordon was a face in the wall, if he wanted Rita dead and all that jazz, he couldve done it himself that badly
I'll admit I haven't seen the film yet, going by what I know in the series backstory.
Perhaps getting emotionally unruly teenagers to work together is more important to Zordon than finishing Rita for good.
It does raise questions about his mentoring though. I have wondered about this myself.
Talking about things like this is fun!