REMOTE_USER authentication can be achieved via a WordPress plugin:

http://dev.wp-plugins.org/browser/http-authentication/trunk/

It uses the WordPress user database, though, meaning you still create users in WordPress.  If this is unacceptable for integration with Zope, I suggest looking at the "pluggable" functions:

http://codex.wordpress.org/Pluggable_Functions

Less editing of upstream source.  :)