My impression is that time-travel had been around long before it was used to escape the supernova. In the past, it was used by the likes of Zhor Khan to banish political rivals and enemies, but it was only recently that it had been put to the purpose of escaping the disaster. I always assumed the era of Zhor Khan was long before the era of Atoz. Certainly, Zarabeth never mentions Atoz . . . .
And, yeah, the way she talks, it does sound like she might have had some sort of personal connection to Zhor Khan, which may explain why he went to the trouble of arranging such a uniquely cruel exile for her. I can't remember the exact words, but she says something like "He had an inventive mind, that one?"
(This is the part where I hint that Sarpeidon plays an important part in my upcoming Trek novel, No Time Like the Past
. . . .)