For example- Christianity has concept of good and evil duality (from Zoroastrianism) which Judaism lacks; Judaism lacks a devil or Satan (Ha Satan in the book of Job is an angel under full control of the Lord doing only what the Lord asks and is not the Christian devil despite Christianity calling him that), Judaism lacks heaven and hell, heaven is for angels not dead people, sheol is more like purgatory a grey nothingness where you have no bodily feelings, the only feeling is a removal of the presence of the Lord (which to any Jew the lack of feeling the Lord's presence IS a kind of hell); Judaism is fully strict monotheism which only Islam shares; Judaism does not have the concept of Original Sin and lacks a real understanding of a concept such as "sin" at all, the 613 laws of the Torah are just that- LAWS not morals that you can "sin" against; it is deeds that matter, not religious thought, belief, or prayer (the boy that recites the Hebrew alphabet at Yom Kippur because he doesn't know the prayers, but does good deeds and is sincere in his heart bends the Lord's ear more than those who prayer in the Temple "correctly"); the Eucarist- can't possibly understand how someone can look at the Eucarist and say "that's something a Jew told them to do"... "Eat this for it is my flesh, drink this it is my body"... noooo, Jewish taboo on canabilism or drinking of ANY blood would make this absolutely something that would have gotten Jesus stoned long before the Romans crucified him, clearly the idea of transmogrification was a later concept by non-Jews; the Talmud clearly states when an abortion is mandatory (to save the woman's life) and that a fetus is not a living human child until the crown of the head passes the "opening", clearly different that Christianity's views (though Christianity's anti-abortion stance is relatively recent in its 2,000 yr history). A lot of the quoting of Scripture from the Old Testament that Christianity does to validate many of their beliefs are taken out of context or poor translations.
Those are just some of the differences between Christianity and Judaism and doesn't even begin to mention the fact that Christians don't follow any of the laws. Other than Christians say "we worship the same god", the two religions are as different as Judaism and Zoroastrianism.
If they are so different then why do you say it is a misunderstood version?
However to begin with, you write as if you have a deep bias and have perhaps a reverence for one over the other. Either ways let's examine this piece by piece.
1. The duality of Good vs Evil in Christianity is unlike that of the Zoroastrian version, in which the world is in a struggle between two opposing forces and that each one is fighting for the souls of one or the other. Christianity (from what I have read) is against this theory completely denounced, as in Christianity it is clear; God does not seek converts in order to defeat an opposing ideology, but for 'his' glory. Therefore Christianity's version of Satan is built from the Jewish version, not a insertion from Iran. If you have proof that the concept of Satan in Christianity came from Iran, please provide it.
2. Heaven and hell you are correct on. But was this version of Heaven and Hell from Iran? The burden of proof is on you.
3. Judaiism as it is preached orthodox is monotheism, but does that mean anything? Same for Islam. I can argue easily how one sect is true and the other is not, who are you to say one is orthodox and its interpretation is correct? As well answering several points in one, do you know that these peoples interpretation is wrong whenever they knew the books, they knew Syriac and had the translation or they themselves knew Hebrew natively. How was the interpretation flawed? Now tell me how these verses where mistranslated by early Christians...
Genesis 1:2 "And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters"
Through the English translation we get the possibility depending upon the lens that you read that the 'spirit' is separate from this God and is in some way a separate entity whether it is subservient matters not, to the Christian this validates his/her belief. Also the word used is Rûach which (I don't speak Hebrew but I can get around lol) "wind" ,"breath", "storm winds", "spirit" it is the same word used for the 'recreation'/renewal of the world following the deluge. Whatever your view is on this word, how could a Christian not see this in Hebrew then turn to the deluge and not make connections?
Exodus 3:2-6 KJV
"[2] And the angel of the Lord appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed. [3] And Moses said, I will now turn aside, and see this great sight, why the bush is not burnt. [4] And when the Lord saw that he turned aside to see, God called unto him out of the midst of the bush, and said, Moses, Moses. And he said, Here am I. [5] And he said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground. [6] Moreover he said, I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob. And Moses hid his face; for he was afraid to look upon God."
So the through this it can be argued that it was the Angel of the Lord who said it was the God as well, the text did not introduce a new figure that is Elohim but it said he called to Moses from the bush from where the Angel of the Lord was. Does this mean that the Angel of the lord is Elohim as well? If not it still begs the question. Either ways this is one of the many instances that the "Malakah YHWH" is something more than a regular Angel, and regardless of your belief or interpretation, wouldn't a Christian looking to validate his belief look at this and say hey that's Jesus? In fact this is what they did...
These are only two out of several for both the Rûach and the Malakah YHWH but I assume you understand the point. Now I have shown instances where a Christian could pull trinity from whether it is correct to you or not. Now the burden is on you show me where Christians where pulling trinity from, after I have shown they pulled it right from the Jewish sources.
4. You should know that the Eucarist refers to a sacrifice that Jesus supposedly paid. While on the surface it is easy to say well cannibalism is taboo in Israel and surely this was addition, that is not entirely the case. Christians will pull up Leviticus 17:11 " For the life of the flesh is in the blood...", so a Christian will say that it is a ritual to commenmorate "the sacrifice/life" of Jesus which was spilled. It is a concept not unlike that found in pre-Columbian Mexico.
5. You are correct on original sin, it perhaps originated in Iraq, but the Tanakh leaves this an open ended question and a Christian/Gnostic can take their own meaning.
Now after all this, Christians use Hebrew text then and now to validate their belief system and find evidence for it in Jewish scriptures, did they do the same for the Avesta? Of course the two are different but the question was which is more alike, Christianity to Judaiism or Christianity to Zoroastrianism.
But to clarify this, this was not to offend anyone and I took a position that either could be right depending upon interpretation, at least if you hold one of these religions.