While some Christians think this prophecy will be fulfilled in our future, I will show why the major theme of Zechariah 12-14 is clearly the destruction of Jerusalem in AD 70 (Zechariah 12:2, 11; 14:2, 11).
First, the big picture. There were three major judgments against Israel by God in history:
(1) In 722 BC, God used the Assyrian army to judge the northern kingdom for her sins. The Jews were dispersed, never to recover.
(2) In 586 BC God used the Babylonian army to judge Judah and Jerusalem. God allowed the return of the Jews from Babylon and restoration of Judah, in part, to maintain the genealogical line of Jesus.
(3) In 70 AD God used the Roman army to judge apostate Israel for her sins (Matthew 23:13-24:2), her failure to accept Jesus as Messiah (Matthew 23:37-38), and her participation with the Roman authorities in Jesus’ crucifixion (Matthew 27:25).
AD 70 marked the end of biblical Judaism. According to Josephus 1,100,000 Jews died during the war (AD 66-70). The temple was reduced to rubble, and along with it, animal sacrifices for sin ended forever. The priesthood has never been re-established after its demise in AD 70. Note the finality of the coming destruction in Zechariah 14:11―”utter” destruction of Jerusalem. There is no hint anywhere in the Bible of a yet-to-be rebuilt third temple or its destruction.
Zechariah was written about 520-518 BC after the Jews returned from captivity in Babylon. Earlier parts of the book are about the events surrounding the restoration of Jerusalem. The prophesied fall of Jerusalem, especially chapters 12-14, could only point to AD 70. The AD 70 devastation of Jerusalem marked the only judgment on Israel future to Zechariah.
The judgment of Old Covenant Israel in AD 70 is found all over the New Testament. In Matthew 21:18-19, Jesus curses the fig tree a symbol for Israel (Jeremiah 24; Hosea 9:10)―promising that she will NEVER produce fruit ever again! Then in Matthew 21:33-45 the Jews admit that Jesus’ parables are about the kingdom soon to be taken from them and given to others―obviously the church. In Luke 21:22 Jesus declared “These are the days of vengeance to fulfill all that is written.” This all happened in the first century.
Jesus’ riding on a donkey (Zechariah 9:9-10) was fulfilled with our Lord’s triumphal entry into Jerusalem (Matthew 21:10-11; Luke 19:28-40). Luke’s rendition is immediately followed by Jesus’ weeping over Jerusalem and the destruction of the temple― obviously all first-century fulfillments. Jesus’ first advent and the destruction of the temple (at Jesus’ Parousia, i.e. his “effectual divine presence in judgment) are portrayed as two parts to the same event. Compare with: Isaiah 61:1-2; Daniel 9:24-27; Haggai 2:6-7 (ref. Hebrews 12:26, 37); Malachi 3:1-5; 4:1-5 (ref. Matthew 3:7-12); Luke 11:29-32; Hebrews 10:11-13.
Zechariah is much about Jesus’ Messianic fulfillment and work of salvation. Zechariah 14:8 mentions “living waters,” which means the blessings of salvation from Messiah, available to all who believe (Isaiah 55:1-5; John 4:10-14; 7:38; Revelation 22:1, 6). Jesus’ living water is not a promise of an event future to us. It is available NOW as a result of Jesus’ finished work.
Zechariah 14 follows two chapters that we should be able to agree that had fulfillment in the first century in Jesus. Compare Zechariah 12:10 with John 19:37. Also compare Zechariah 13:7 with Mark 14:27.
The Lord said He would “gather all nations against Jerusalem to do battle” (Zechariah 14:2). 1st century Rome was an empire consisting of all the nations of the known world at the time (see: Luke 2:1). The Roman Empire “extended roughly two thousand miles from Scotland south to the headwaters of the Nile and about three thousand miles from the Pillars of Hercules eastward to the sands of Persia. Its citizens and subject peoples numbered perhaps eighty million.”  The siege of Jerusalem actually included a League of Nations, under Roman dominion, consisting of Italy, Achaia, Asia, Syria, Egypt, Africa, Spain, Gaul, Britain and Germany. This more than satisfies the textual requirement of “all nations”– especially when this term (and similar terms) is oftentimes much more limited in scope in its scriptural usage (e.g., 1 Chronicles 14:17; 2 Chronicles 32:23; 36:23, Ezra 1:2; Psalm 118:18; Jeremiah 27:7; 28:11; Habakkuk 2:5).
The atrocities mentioned (“houses plundered” and “women raped” in Zechariah 14:2), certainly fit the scenario of the Roman siege of Jerusalem. Zechariah tells us that “half of the city shall go forth into captivity” (14:2). Accordingly, Josephus speaks of a surplus of Jewish slaves. The “number of them that were slain was so great that the very soldiers grew weary of killing them” and “sold the rest of the multitude, with their wives and children, and every one of them at a very low price. . . . and indeed the number of those that were sold was immense. . .” 
After the “final judgment” of Zechariah 14, there are still people who do not worship the Lord (14:16-17)—so it cannot be the end of history. Zechariah 14 is a parallel to Isaiah 65-66, where we see that (a) regular human history continues after “Armageddon” as there are births, deaths, building, etc. (b) there are still people living on earth who never heard of God, and (c) the survivors of the final judgment evangelize those who never heard of God.
Now let’s consider some difficulties or objections:
- Zechariah 14:4-5. This passage mentions that, at the coming of the Lord, the Mount of Olives is “split in two.” Futurists think that has not happened yet. But we should note that this is standard, non-literal Hebraic apocalyptic language. It is common in the Old Testament to see poetic descriptions of disruptions of the created order at God’s judgments. See Isaiah 13:10-13 (against Babylon), Isaiah 34:4-10 (against Edom), Jeremiah 4:23-31 (against Judah and Jerusalem), Ezekiel 32:7-8 (against Pharaoh and Egypt), Joel 3:15-16 (against the nations), Amos 5:20, 8:9 (against Israel), Micah 1:2-16 (against Israel and Judah), Zephaniah 1:14-18 (against Judah, Jerusalem, and Judah’s enemies). Further, Jesus placed his coming in judgment (with his angels) against Old Covenant Israel in his own generation (Matthew 10:23; 16:27-28; 23:35-36; 24:29-34; 25:31; 26:64).
- Zechariah 13:8 says that “two-thirds will be cut off.” Futurists think this means a future time when two-third of Jews will be killed. I can hardly imagine a more anti-Semitic interpretation. But remember that numbers in the Bible are often figurative. Yet, Josephus reported that over million Jews were killed in Jerusalem in AD 70, so the two-thirds number may fairly represent the number killed.
- What about Zechariah 12:9, which says God will destroy all nations that come against Jerusalem. The Roman army was not destroyed in the first century, so how was that fulfilled? In biblical interpretation the less clear or seemingly contradictory passages should be interpreted in light of the clearest and most dominant ones. The New Testament teaches that there was Old Covenant Jerusalem which was to be destroyed by the Romans in AD 70, but the NEW Covenant Jerusalem lives on (Galatians 4:21-31, Hebrews 12:22-29; Revelation 21). This is the spiritual kingdom of Christ. Zechariah 12:9 must be teaching that whoever opposes Christ in the New Covenant, will be destroyed. Zechariah 12:2, 11 and 14:2, 11 were definitively fulfilled at AD 70 when Jerusalem fell. So, Zechariah 12:9 is about God’s future enemies of Christ, not the Roman army. Then everything in Zechariah 12-14 is reconciled to a first-century fulfillment.
Here is a helpful article by Robert Cruickshank for further study:
Also, see this article by Gary DeMar:
 Flavius Josephus, The Wars of the Jews, 6.9.3
 Otto Friedrich, The End of the World: A History (New York: Coward, McCann and Geoghegan, 1982), 28.
 Josephus, The Wars of the Jews, 6.8.2