Save Shadowheart > Press K > Take the Command spell > Use Command on Commander Zhalk to drop the sword > Pick up the sword with Lae'zel = SMASH!
Did this on Tactician difficulty where Zhalk has 195hp with two attacks per turn and had no issue killing everyone, except the two cambions, so killed both the Commander and the mindflayer along with every minion in the room and looted all the corpses before running away. Plus I did so before turn 8 which was surprising
Naturally some luck is involved depending on the mindflayer landing its hits, that is why buffing him with Bless or Guidance via Shadowheart is important.