I can't help with the htaccess redirect and its effect to the normal Zenphoto behaviour.
The easiest besides htaccess would be a simple php header redirect. Clear the themes index.php file and place something like
`
<?php
header("HTTP/1.1 301 Moved Permanently");
header("Location: http://www.yourdomain.com/zenphoto/<desired album>");
header("Connection: close");
?>?>
`
in the first line. More info about details on this on the web..:-)