Having 3 HDD and 3 SDD is not possible to create a fusion pool with having RAID-z for both vdev and medatata.
1. Create the vdev with RAID-z and 3xHDD
2. Select the 3 SDD for metadata but only stripe and mirror type are available to be selected while raid-z option is not available.
Still, "Metadata vdev must be the same type as the data vdevs. First data vdev is a raidz, new Metadata vdev is a stripe." warning is diplayed.