it appears this line in zendesk.module needs to be changed

drupal_goto('user', 'destination=services/zendesk');

needs to be changed to this.

drupal_goto('user', 'destination='.urlencode('services/zendesk'));

I guess you could save the cpu cycles you could do this.

drupal_goto('user', 'destination=services%2Fzendesk');

otherwise you end up with breadcrumbs that look like this Home > User?destination=services > Log In, in reality its a bug in drupal (should break at the ? in parsing page paths) but easily handled in the module.