Interac and ZellePay sound very similar indeed. The only difference being that you have to have set up a ZellePay account on both ends of the equation and the deposit is always instant. The biggest problem with this system, if you consider it one, is that the transaction is instant and cannot be recalled once you've completed it, so you need to be absolutely certain you haven't fat fingered the email address of your recipient. If you do, the transaction will fail if that address does not have a ZellePay account, but if it happens to be associated with one that money is in that address's associated bank account the moment you hit the button to pay them.
And, as you noted, you can associate a mobile phone number with a given bank account along with an email address or instead of an email address.
I've had a PayPal account for decades (plural, I think, but definitely well over 10 years if not) but haven't established a ZellePay account because it's just not nearly so popular in the USA. I have one client, and a senior citizen, who uses it and loves it and asked me if I accepted Zelle payments the last time I did a job for her.
Brian - Windows 10, 64-Bit, Version 21H1, Build 19043
It is the function of creative men to perceive the relations between thoughts, or things, or forms of expression that may seem utterly different, and to be able to combine them into some new forms--the power to connect the seemingly unconnected.
~ William Plomer