The problem with all of the New Testament and much of the Old Testament is that it has been altered over time again and again. While for some texts in the old bible there is good reason to assume them to be reliable, a lot is not.

Especially the New Testament is clearly a product of trying to mix abrahamic faith with pagan beliefs. You can see this in the concept of trinity and Jesus being the literal son of god. This directly contradicts the commandments given to Moses and Allah has rejected it again in the Quran. Also these concepts were not of the time of Jesus, but developed some hundreds year after. It is also contradictory to much the New Testament says about the life of Jesus, as he was explicit not to speak in his name, but in the name of God.

This is very different to the Quran, where already at the time of revelation much effort was made for preservation in the original form, as well as the life of the prophert Mohammed being documented too.