Domain point to a subdomain

[apinto]

It's very easy to do that.
First you add abc.coom domain (or add it as a shared domain that will allow abc.com to be used by all accounts to create subdomains).

Than you create the subdomain xyz.abc.com
On the public_html folder of that subdomain you create a htaccess file that redirects ot the domain you want.
You can use http://www.htaccessredirect.net/ to generate your file fi you are not sure about how it is done.

The above steps are true, either for a subdomain or a regular top level domain (abc.com)

Also, if you need to create the subdomain first, it will work exactly the same way, however it will be redirected to a error page (because domain does not exist)