groupmems: invalid option -- 'Z'
Usage: groupmems [options] [action]

Options:
  -g, --group groupname         change groupname instead of the user's group
                                (root only)
  -R, --root CHROOT_DIR         directory to chroot into

Actions:
  -a, --add username            add username to the members of the group
  -d, --delete username         remove username from the members of the group
  -h, --help                    display this help message and exit
  -p, --purge                   purge all members from the group
  -l, --list                    list the members of the group