zrok.io today supports private shares: Private Shares | Zrok. A private share does not have a public address, and can only be accessed via zrok
zrok.io today supports reserved shares: Reserved Shares | Zrok. A reserved share lets you set the name of the share a client uses to access it. E.g., https://MYRESERVEDSHARENAME.share.zrok.io
We are currently working on a "dedicated custom domain" for the hosted zrok offering, which will allow you to configure your own custom replacement of the ".share.zrok.io" part of the URL