If it is a scam, it will be a run of the mill fake payment scam where "Zelle" requires that the scammer needs to send you more money (which they will spoof a picture) to upgrade your account to a business account, and then once your account is a business account, you send the money back.

What I don't get is in what universe, people would believe that they're going to have a stranger trust them and send several hundred dollars because "Zelle" told them they needed to. And that they will trust that this person will send this money back.

Where would this actually work in real life?

Its just a new(er) iteration of the doubling money scam in Runescape from like 2006.