AppleShare File Server recognizes hard-drive partitions, depending on how
well-written the partitioning software is. There are probably some
partitioning utilities that are not compatible with AppleShare. Contact the
utility's vendor to make sure it works.
In the larger picture, you can't specify login privileges based on zone,
but you can do the same thing by setting the privileges based on user ID.
The login list is specified by volume, so you can give each volume a list
of "good" users and by telling it to disallow "guest" log-ins. This will,
in effect, do what you need.