Zwift User Name?

I was planning registering for this E-Fondo series, but it asks for the user name not the Zwift ID. Dumb question, but what user name are they talking about?

I would guess it is this one, found on The at Home Cycling & Running Virtual Training App .

If there is a comment section on that form, I would but your Zwift ID in there too- if you go to your Zwiftpower profile it will be the number on the end of the url.
zwiftpower com/profile.php?z=148665 for example

Hey, I am wondering if they require user id or username? I am not able to find my username…