We will kill billions of people in the first four verses, but there’s also a blessing that cannot come without this horrifying event.
Like Ezekiel 38 and 39, Zechariah 12 and 13 are a single vision. Stephen Langton, the Roman Catholic Archbishop of Canterbury, broke this vision into two pieces, and was very foolish in doing so. And, putting that artificial break in the middle made it harder to see that Zechariah 14 is not connected at all to the previous two chapters. Chapters 12 and 13 begin with an attack upon Jerusalem and the region of Judah. It continues with their repentance and the acceptance of Jesus as their savior. Zechariah 14 is a completely different story.