In his essay entitled “Prophetic Movements and Zealots,” James D.G. Dunn discusses the Zealot movement. He explains that the Zealot movement was a violent revolutionary movement against Rome that emerged in Jerusalem during the winter of A.D. 66-67. Thus, when Luke 6:14-16 list the twelve apostles and mentions in v. 15, Σίμωνα τὸν καλούμενον Ζηλωτὴν (Simōn ton kaloumenon Zēlōtēv) meaning Simon the one being called a Zealot, Dunn argues that this is not referring to Simon being part of the Zealot movement because this movement developed much later. From this perspective, Simon being called a Ζηλωτής (Zēlōtēs) Zealot was an extra personal name used to distinguish him from Simon Peter  and to describe him as zealous or ethusiastic for God and his law. However, Dunn also mentions that “the fourth philosophy” movement had similar, yet non-violent, views as the Zealot movement. The fourth philosophy movement was a Pharisaism division led by certain teachers (e.g. Judas the Galilean, Saddok, etc.) who took a firm, proactive attitude against Roman rule. This movement developed in response to the census and taxation implemented by the Roman official Quirinius in A.D. 6-7. The views of the fourth philosophy continued for the next several decades and then bubbled up to form the Zealotism that Josephus describes as leading to the war. Therefore, while Simon may not have been called a Zealot in the A.D. 66-67 (and beyond) sense of the term, Simon may have been called a Zealot in the fourth philosophy sense, meaning that he had a strong zeal for the God of Israel and a fiery political zeal against Rome.
 James D.G. Dunn, “Prophetic Movements and Zealots” in The World of the New Testament: Cultural, Social, and Historical Contexts,eds. Joel B. Green and Lee Martin McDonald (Grand Rapids, MI: Baker Academic, 2017), 247.  Ibid., 250.  BDAG, “Ζηλωτής”  TDNT, “Zēlos, Zēloō, Zēlōtēs.”  Dunn, “Prophetic Movements and Zealots,” 248.  DNTB, “Revolutionary Movements, Jewish.”  Dunn, “Prophetic Movements and Zealots,” 248.  Ibid., 248-249.