Can Zeno even be hurt?
Otherwise something like L and Light teaming up and convincing Zeno to erase himself is the only way to punt (get it...helmetball head) it out of existence. Not sure how though...can Zeno even feel sad? Can't get Hey Arnold to do some heinous crimes, film them with a grainy camera and then convince Zeno it was Zeno to make him erase himself (tbh I'd feel bad...then remember it erased whole universes...although is it that bad to erase them, if they don't even know about it so didn't suffer in the process? I guess they lost their opportunity to live). Maybe they can convince it to erase itself by lying and saying something really fun happens only if the head of the universe is erased and lie that it can be undone...but if the plan fucks up and it just comes back after a week or something and nothing fun happened then someone's getting erased, so gotta plan something fun just in case, but idk what. Ninja Murasaki slapstick routine? Have Vegeta and Whis learn to do this:
wonder who made this all those years ago. Some unknown legend.