You are probably asking about the zebra server then.  I've setup three instances on my servers where zebra runs on a different server than the staff interface.  I changed three things to get mine working.  First is the listen tags.  Each listen tag has to have a unique port across all of your zebra instances.  So I ended up with six different ports in use by zebra.  Second is the port number in the server/explain/serverinfo tag for each server.  I don't know if this is important, so I changed it to match the listen tag.  Last, each server has an associated serverinfo tag where the user and password is defined.  I would strongly recommend changing these from the default to something else.