Problem solved.
It is necessary to mount a share, not a directory. According to smbclient -L zaurus, home is a share, not home/zaurus (which is what I had specified in the mount command). When I specified home in the mount command, it worked:
mount -t smbfs //192.168.129.201/home /mnt/zaurus -o password=""
Note that it was not necessary to add any lines to smb.conf (nor to change it from the default in any other way).
I am still troubled that ping <client> from the Zaurus produces the error message "Network is unreachable". Any idea what that's about?
Thanks to everyone for the advice.