ZFS: Change zfs mirror pool to a mirrored vdev in another pool

[ronelld.regen]

Good morning FreeBSD community.
I have a question on ZFS data handling and couldn't find anything on the Internet (alternatively I am too stupid).

My task is the following:
I have 2 separate zfs mirror pools, with data on it.

Code:

  pool: zfs_r1
 state: ONLINE
config:

        NAME        STATE     READ WRITE CKSUM
        zfs_r1      ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            md0     ONLINE       0     0     0
            md1     ONLINE       0     0     0

  pool: zfs_r2
 state: ONLINE
config:

        NAME        STATE     READ WRITE CKSUM
        zfs_r2      ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            md2     ONLINE       0     0     0
            md3     ONLINE       0     0     0

I want to connect them to one data pool with two mirror vdevs, looking like

Code:

  pool: zfs_r1
 state: ONLINE
config:

        NAME        STATE     READ WRITE CKSUM
        zfs_r1      ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            md0     ONLINE       0     0     0
            md1     ONLINE       0     0     0
          mirror-1  ONLINE       0     0     0
            md2     ONLINE       0     0     0
            md3     ONLINE       0     0     0

By detaching md3 from zfs_r2 and adding it to zfs_r1, I loose my data.
Is there a way a "moving" the md2/md3 mirror to a vdev in another pool?
Thank you for your help and your recommendations.
Kind regards, Martin.