You are taking a strange detour again.
The evidence that Jesus was a legend is doubtful and even most unbelievers don't believe it. Jesus Vs Zoroaster – Debunking The Alleged Parallels | Reasons for Jesus
8. Zoroaster’s followers expect a “second coming” in the virgin-born Saoshyant or Savior, who is to come in 2341 CE and begin his ministry at age 30, ushering in a golden age. I have been able to confirm that this is true to some extent: a return is expected in 2341 CE, to start a golden age; the details on age 30 I have found nowhere. Whether this future Deliverer would indeed be Zoroaster himself again is indeed something that has been interpreted, but later Zoroastrian texts think that the person will be of the line of Zoroaster, not Zoroaster himself. [Wat.Z, 94-5]
There is no significance between Zoroaster and the age of 30. Even the belief about a future Messiah in Zoroastrianism is different from Christianity. The belief in his second coming is not a consistent doctrine in their faith. The second coming of Jesus is believed by both Catholics and Protestants. The Bible is not vague about the second coming of Jesus. Jesus said in John 21:22, " If I will that he tarry till I come, what is that to thee? follow thou me."