What’s with the similarities and why do you think that it might have strongly influenced Medieval Christians as these findings might show?
Some people have been searching into its history and relationship with Christianity, with some interesting finds. Its implied that the European Zoroastrians all converted to the Catholic or Orthodox Faith. The last prince of the Zoroastrian Sassanian Empire converted to Christianity after its fall, and Piruz Navandhi was a Zoroastrian who considered the idea of Jesus being the Messiah while holding both Christian - Zoroastrian beliefs simultaneously. These brand of Zoroastrian converts might have strongly influenced Medieval Catholics or Christians and resulted in the popular strand of the time.
Even Catholics in the countryside during the Middle Ages continued to hold Zoroastrian strains alongside their Christian beliefs and it influenced their superstitions. The devil was an individual who roamed the landscape causing trouble and issues, sometimes even causing people to be born with inherently dark qualities that gave them an evil nature. If you study Zoroastrianism you will find the foundation that they had, it wasn’t just ‘paganism’ but Zoroastrianism that came before the Church.
On the religion’s teachings for context:
Zoroastrianism predicted before Christianity came into place of a virgin birth even that would bring forth a messiah who would oversee the resurrection, destruction of the evil one and all evil in the world. Many Zoroastrian converts to Christianity who believed Jesus to be the messiah in their beliefs strongly rejoiced at the notion that the ‘Saoshyant’ (Saviour) predicted had already come to our world. The religion historically it has a pontiff or pope just as the Church does, but the last one in Iran is deceased and the Zoroastrian pope’s office has been empty since. They believe in saints and angels as well just as Catholics do, and also in a holy spirit?
Their theology teaches that God isn’t necessarily all powerful and did not create bad. Evil is a separate thing from God unless you believe in the interpretation that ‘Zoroaster meant bad vs good mind and got misinterpreted’. Its that our purpose in life is to push bad against the bad as ‘God the Wise Lord’ with hopes of eventually having an environment where goodness or good thoughts can flourish and where evil cannot tempt us into sinning. Environments shape people etc, and an evil environment infected by the devil will corrupt. The devil makes war against the good but will be destroyed in the end times when the messiah comes.
In the approach to evil it does not teach ‘turning the other cheek’ and teaches that people should resist, in attempt to vanquish the bad in their lives through whatever means are reasonable.
So apparently the original version of the religion never opposed conversion and there are denominations outside of the Parsi ones that allow it with some Parsis or Priests also joining their side recently.