Copy a ZFS Volume as a disk image

dd if=/dev/zvol/rpool/data/base-201-disk-0 of=win2k19.raw bs=1M

/dev/zvol/rpool/data/base-201-disk-0 is the disk file

win2k19.raw is the RAW disk file which you need to convert according to your needs (vmdk, qcow2 etc)