Zelle was a consortium of the biggest US banks. It works fine if you have a deposit account at one of those institutions, or if you have created a Zelle account that lets them get you funds through a shim if your bank isn't a member participant of Zelle. If you're at a brokerage that doesn't support it, a credit union, or a community bank, your experience is meh or non existent.

FedNow is native real time messaging plumbing, so all deposit accounts can support it once you plug into FedNow (which is run at cost by the Fed). We should theoretically arrive at an experience similar to UPI, PIX, and other instant payment systems where you can use phone numbers, email, or QR codes to facilitate payments over the next 1-3 years.