An ancient star faring race that once was common in the Galaxy 1 million years ago and fought a genocidal war with the "Bugs". It is believed that the cost of that victory was was a technological fall.
We now understand that the Zak are the Tzen. There has been some evolution but the species is still recognizable.
The recent recovery of an ancient sleep tube from a Tzen/Bug battle site recovered one survivor. A tour de force of the medical art and plain dumb luck. The Zak medical team that performed the recovery said as much. She is recovering from her ordeal and teaching as much as she learns. For her sake the Zak are not so different that she is alone.