Redirects are a separate option on cPanel.
Having looked at them though, I'm not sure they are exactly going to work as you want (give it a try though, as its the easy option. Set the redirect to temporary to check it works before changing to permanent).
You might want to delve into using mod_rewrite to do it.
So in the .htaccess file (create this file if it doesnt exist) in the public_html folder you'd put something like:
Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^xxxxx\.myzen\.co\.uk [nc]
rewriterule ^(.*)$ http://www.myparkeddomain.com/$1 [r=301,nc]
The entry ^www\.xxxxx\.myzen\.co\.uk is a regular expression - hence the need to put a ^ at the start and a backslash before each dot.
[nc] means that case gets ignored
r=301 tells browsers (and search engines) that this is a permanent redirection. Before uploading a version of this set the last bit of the 2nd line to just [r,nc], and when you've checked its working properly change it to [r=301,nc]
NB I extracted this information from
http://corz.org/serv/tricks/htaccess2.php . You might want to have a quick read there.
Kindest regards,
James Sweet
http://www.zen.co.uk