Yes! They will receive a notification via email or text message.

Money sent with Zelle is typically available to an enrolled recipient within minutes1. If you send money to someone who isn't enrolled with Zelle, they will receive a notification prompting them to [...]

You can only cancel a payment if the person you sent money to hasn't yet enrolled with Zelle. To check whether the payment is still pending because the recipient hasn't [...]

In order to use Zelle, the sender and recipient's bank accounts must be based in the U.S.