dd zero on the wrong disk. ZFS over GELI on that disk, recover possible?

[Stefano Rossi]

Hello,

I made a tremendous mistake with a "dd of=/dev/zero of=/dev/ada1" command. ada1 was the wrong disk.
The command was interrupted after a few seconds (I only wanted to erase the partition table), and a "gpart create -s gpt ada1" was given before I realized my mistake.
On ada1 there was a single partition, type freebsd, which was labelled HD4. /dev/label/HD4 was geli encrypted with a keyfile (I still have the keyfile), and /dev/label/HD4.eli was a zpool (named HD4 too).

Is there any way I could save at least some of the data on that zpool? I know geli makes backup of the metadata, I must have them somewhere on my root partition.

Is there any way to recover the few lost megabytes at the start of the disk?
Or, would it be possible to recreate the same partition table with the single partition, relabel it and restore the geli backup to the labelled partition? Would then zfs recognize it?

Please, if you have any idea share it with me, the data on that disk is vital.

Thank you very much.
Stefano Rossi