OK, still trying to understand:
$ zfs create zfszero/DOCKER
$ incus storage create docker zfs source=zfszero/DOCKER
Storage pool docker created
$ incus storage volume create docker docker
Storage volume docker created
$ incus storage volume set default docker zfs.delegate=true
Error: Storage pool not found
$ incus storage list
+--------+--------+----------------+-------------+---------+---------+
| NAME | DRIVER | SOURCE | DESCRIPTION | USED BY | STATE |
+--------+--------+----------------+-------------+---------+---------+
| docker | zfs | zfszero/DOCKER | | 1 | CREATED |
+--------+--------+----------------+-------------+---------+---------+
What am I doing wrong?