Double edged sword IMO. If you use Zelle and off a digit in a phone number or email you are out of luck. No way to recover funds once sent.

If you send it to an email address that doesn't exist, does the transfer go through? If so who ends up with the money?

It's been a while since I sent funds to a new address but I am pretty sure my bank's UI provided protection against that, and now when I send future funds to the same account, I just pick them from a drop down box instead of entering it manually.

No - it’s more dangerous with a phone number, which is how I usually send/receive.

Much, much safer way to use Zelle is to ask the receiver to request a payment from you and then accept the request.

That's a good idea in both cases.

Although I'm guilty of just sending funds direct but only through email addresses which I usually copy / paste straight from what someone wrote to me.

It cancels after a few weeks (IIRC) of remaining unclaimed.