Hello Dean,
What's reference for the text you quote, or is that what you are asking?
As you know the sources for Zarathustra's birth stories are the Middle Persian accounts, and among those Book 7 of the Dēnkard stands out. The birth story is complex and Ohrmazd and his helpers put many elements in motion so that Zarathustra can be conceived. One of these, is sexual intercourse between the parents, something the the daemons try to discourage.
Best,
Arash
Sorry for once again spilling over the South Asian borders but I can't seem to find a reliable reference for this claim:
"Zoroaster is said to have had a miraculous birth: his mother, Dughdova, was a virgin who conceived him after being visited by a shaft of light.
Perhaps some of our Indo-Iranians might know.
Best,
Dean