Having messed with zfs: failing to import pool

I did set the mountpoint of a cloned and promoted ZFS dataset to "/" resulting to get the error probably because two datasets now have mountpoint "/"
internal error: failed to initialize ZFS library
to any zfs and zpool commands.

How to fix this? System is still running, but no zfs commands are possible.
This has happened to me a few times. Rebooting into Single User mode and resetting the demoted dataset mountpoint to 'none' might fix it. I'm no ZFS expert, though.
I don't have a solution but, if you can import it on readonly mode, you can make a copy of your data and build a new pool.