Link von Domain zu Wordpress-subdomain mit customized page

Hello,

I have got a Wordpress site running on my own webspace (all mentioned domains registered via one hoster). There is a Wordpress blog in my domain, e.g. "blog.mysite.zzz" and a Wordpress customized page (blog with different theme) in a subfolder (somehow configured, not an existing subfolder on my webspace but it shows you the second blog), e.g. "blog.mysite.zzz/custom"
I want an additional domain ("e.g. www.blogzzzsites.zzz") to link to the above mentioned site "blog.mysite.zzz/custom"
How can I establish that?

Furthermore, is it possible to configure the domain link in the following way:
If you click on www.blogzzzsites.zzz and click on links in the following blog, still "www.blogzzzsites.zzz" is being shown as root domain and not "blog.mysite.zzz/custom"?

Thank you very much in advance.
Kind regards