“After all, Christianity is an amalgam of Judaism and Hellenism/Platonism (with a tinge of Zoroastrian spice) and that’s a pretty immiscible combination.”
I’d have to disagree with that statement. Christianity isn’t an amalgam of anything. Paul used arguments designed to appeal to Gentiles, who wouldn’t have understood arguments based on Jewish Scriptures, but the ideas he taught didn’t come from the Greeks, he merely put the ideas in language they could relate to.
As for the Zoroastrian angle, this is a pretty recent ploy by secularists to try to invalidate Christianity, but there’s really no evidence to support it. Zorastrianism itself is a religion that borrowed concepts freely from other religions, so any superficial similarities to Christianity could have been transferred in the opposite direction. However, even granting that the similarities existed prior to Christianity, doesn’t prove a common origin, anymore than some superficial similarities between Judaism and some Egyptian or Babylonian religous ideas means Judaism is an amalgam of those religions.
There is a lot more to Christianity than Paul, although for most Protestants he is pretty much it. That's pretty lofty for a man Thomas Jefferson described as the "first corrupter of the doctrines of Jesus" and a man who describes himself as "all things to all men."
Paul was not so much a Hellenizer as he was an antinomianist. The only thing Paul did as far as Greek paganism was concerned was to let them off the hook as regards circumcision (which the Greeks thought was silly), and dietary laws. He knew very well the Greeks would never buy into this resurrected Jesus story he was preaching if that included Jewish dietary laws, and Jewish mitzvot in general, including the circumcision.
But the Hellenization of the Jewish sect of Jesus followers comes with John at the end of the first century, when Judaism clearly rejected any and all Christian books and teachings and called Christians apostates and usurpers (minims). Until John there is not a trace of a Platonic Jesus as a Hellenic god; but therefater Palotnism rules.
As for the Zoroastrian angle, this is a pretty recent ploy by secularists to try to invalidate Christianity, but there’s really no evidence to support it.
Uh, I knew the secularist ploy card was going to come up sooner or later. Zoroastrianism actually influenced post-Babylonian Judaism (at least the apocalyptic types, such as Essenes, or Jesus himself), who believed in "resident evil" (otherwise unknown to Judaism until then), the rebellious devil, and what not. The Jewish Christians thus carried Zoroastrian beliefs to the Gentile converts and Gentile Christians merely inherited them from their Jewish counterparts.
Zoroastrian dualism creeping into Judaism has been known for a long, long time and is not a recent "secularist ploy" to discredit Christianity. Christianity can do that all by itself without anyone's help.