I used to be a very avid reader: many books, but can’t remember exact title, author, and other information.

Your source seems to take a common path of not acknowledging the Zoroastrian connection to Christianity. I think this is common and deliberate practice of Christian historians. Don’t mention anything good about religions outside of the Judaeo-Christian realm.

As for the “myth” that Jesus’ family moved to the east, stayed for 15–20 years, and returned for his ministry, I’ve only read one source on that hypothesis. The argument was well presented, but without support from other scholars we should be careful.

On my bucket list is to read the Gnostic Gospels.