What exactly is zeitgeist? I had never heard of it before I discovered Orthodoxy.
It is a conspiracy theory documentary, part of which tries to show Christianity has copied every facet of its belief from earlier religions. The sad thing is, every parallel it draws they have literally made up out of nothing. It seems convincing to those who have no knowledge of the religions they are saying these myths exist in, but to those who do it simply falls flat. They say things like Dionysus was crucified, where there is nothing at all you can find that comes close to that.
I'm most familiar with the inaccuracies concerning Hinduism, and here's an example of how much they simply made up: They say Krishna was born on December 25 - when Janmashtami, his birthday celebration, is in July. They claim he said he was the 'son of God' or 'only begotten son of god' when these words appear nowhere in the Puranas or Srimad Bhagavatam. They say his mother Devaki was a virgin when she had at least five children before him. They say Kamsa killed all the children in the town like Herod did, but he didn't - Kamsa knew Krishna was going to be born to Devaki and kill him so Kamsa kept killing her
children. They say Krishna had a ministry like Jesus, where there is simply nothing like that in the Hindu texts - Krishna only ever told one person, Arjuna, that he was God. They even claim he was crucified - the actual story about his death is a hunter thought he was a deer and tried to shoot him, and he simply disappeared altogether.
Honestly, if their 'scholars' have any actual credentials they should be stripped of them with prejudice.