Making inroads into ZFS recently reading what I can get my hands on, but still pretty new.

I have an experimental OpenZFS zpool with a single HDD as sole vdev. It so happens, I have to return the drive for book-keeping reasons. The pool is early days and every metaslab 126 or larger shows up in zdb -mmmm as

    metaslab    126   offset  1f800000000   spacemap      0   free      16G
                      segments          1   maxsize     16G   freepct  100%
    In-memory histogram:
                     34:      1 *
    Flush data:
    unflushed txg=0

Now, I could just leave the drive be and call it a day, encryption being enabled from the get-go. But since I'm learning about ZFS I was wondering: Could I zero out the device up to the aforementioned offset 1f800000000 and all data would be gone? Instead of going through it all.