Judaism
Christianity was originally a sect of Second Temple Judaism, but the two religions diverged in the first century. The differences between Christianity and Judaism originally centered on whether Jesus was the Jewish Messiah but eventually became irreconcilable. Major differences between the two faiths include the nature of the Messiah, of atonement and sin, the status of God's commandments to Israel, and perhaps most significantly of the nature of God himself. Due to these differences, Judaism traditionally regards Christianity as Shituf or worship of the God of Israel which is not monotheistic. Christianity has traditionally regarded Judaism as obsolete with the invention of Christianity and Jews as a people replaced by the Church, though a Christian belief in dual-covenant theology emerged as a phenomenon following Christian reflection on how their theology influenced the Nazi Holocaust.
Zealots
Josephus' "Jewish Antiquities" states that there were three main Jewish sects at this time, the Pharisees, the Sadducees, and the Essenes. The Zealots were a "fourth sect", founded by Judas of Galilee (also called Judas of Gamala) in the year 6 CE against Quirinius' tax reform, shortly after the Roman Empire declared what had most recently been the tetrarchy of Herod Archelaus to be a Roman province, and that they "agree in all other things with the Pharisaic notions; but they have an inviolable attachment to liberty, and say that God is to be their only Ruler and Lord." (18.1.6)