Most Bible students recognize the word Pentateuch as referring to the first five books of the Bible, which are also known as the Torah, the Law, and the Books of Moses. Muslims, Samaritans, Jews, and Christians have historically credited Moses with being the human instrument God used to write them. If that is not enough evidence, Jesus referred to the Law as being the work of Moses many times (Matthew 19:7; 22:24; etc.). Anyone denying the books as being from Moses probably denies the entire Bible, and quite frankly, I doubt that they would be reading this.
Although I have never heard anyone refer to the first five books of the New Testament as a Pentateuch, in many ways, they resemble that of the Old Testament. For instance, both contain a book that begins, "In the beginning..." (Genesis and John). Both contain genealogies of the same family (Genesis, Matthew, and Luke). Both speak of man's need for a Savior (all five). Both view the Law as being paramount (all). Both refer to the Lamb as being God (Genesis 22:8 and John 1:29, 36). Both speak of Noah, Lot, Abraham, etc. Both depict miracles. There are probably hundreds of other similarities, but I am limited by space and memory.
There are differences that even suggest a similarity. There are two covenants: Law and Grace. Two kinds of sacrifice for sin: animal and that of Christ. Two appearances awaited: one for His coming and the other for His second coming. Two histories: one of Israel and one of the Church. Two extremes of time: one depicts the beginning of time and the other the end of it. Two events of world destruction: one by water and the other by fire. Two groups of twelve: the son's of Jacob and the Apostles. Again, space and memory.
Jesus is alluded to as the Creator in the Pentateuch [compare Genesis 1:1 (Elohim - plural form for the one God) and John 1:1-3; 1 Corinthians 8:6; Colossians 1;16; and Hebrews 1:1-2)]. The Corinthian reference clarifies that creation occurred for the Father, and by the Son. The Father wanted creation, the Son created, and the Holy Spirit gave all living things life (Genesis 2:7 and John 3:5-8). Remember, the Greek and Hebrew words translated Spirit also means breath and wind.
I would never suggest that we name them Pentateuch One and Pentateuch Two, but their obvious relationship clearly shows they are from One Author. They reinforce the authenticity of the Word of God. We are so blessed to have His Word, and hopefully all of my readers have Him as their Lord and Savior. Amen.