Hystaspes (the Greek form of the Persian Vishtaspa) can refer to two individuals:
A semi-legendary king (kava), praised by Zoroaster as his protector and a true believer, son of Aurvataspa (Lohrasp). The later tradition and the Shahnama of Firdousi makes him (in the modern form of his name, Kai Gushtasp) a "king of Iran". As Zoroaster probably preached his religion in eastern Iran, Vishtaspa must have been a dynast in Bactria or Sogdiana. The Zoroastrian religion was already dominant in Media in the time of the Assyrian king Sargon (c. 715 BC), and had been propagated there probably in much earlier times; the time of Zoroaster and Vishtaspa was traditionally put at c. 1000 BC.
A Persian, father of Darius I, under whose reign he was governor of Parthia, as Darius himself mentions in the Behistun inscription (2. 65). By Ammianus Marcellinus, xxiii. 6. 32, and by many modern authors he has been identified with the actual historical protector of Zoroaster, which runs counter to the traditions of Zoroastrianism itself.
Hystaspes' birth year can be deduced from the fact that his son Darius was born c.550 BCE; Hystaspes must have been at least fifteen years old and we can assume that he was born before c.565 CE.
The rebellion spread to the north to Armenia, to the west to Assyria and to the east to Sagartia and Parthia.
This Hystaspes is not to be confused with his namesake Hystaspes, who is mentioned in the Avesta, although the mistake was already made in the fourth century CE (by the Roman historian Ammianus Marcellinus, Roman history 23.6.32).
The role attributed to Hystaspes in the frame story of the Oracle is indicative of an environment where Iranian traditions were well known and were in use in anti-Roman propaganda.
Although Sefer Zerubabel, like the Oracle of Hystaspes and other apocalyptic writings, refers to a chain of world kingdoms, in Sefer Zerubabel the links are not connected, that is, one kingdom does not defeat the other but each kingdom is defeated by the people of Israel.
To conclude: Qumran and the Oracle of Hystaspes point to the strong hold of the belief in the figure of the son of David as a savior, primarily as taking a role on the battlefield.