I do not know zpFocus, but if it has a `password.php` script you can modify it to include a link to the registration page. If it does not have such a script, you can copy the one from zp-core folder to the theme folder. You will probably have to style that script, though. It is bare-bones since many themes provide their own styled version.
What happens with the "I forgot my ... link"? If the user has no e-mail nor pass phrase then the link cannot help him.