Zechariah 14:5
And ye shall flee to the valley of the mountains; for the valley of the mountains shall reach unto Azal: yea, ye shall flee, like as ye fled from before the earthquake in the days of Uzziah king of Judah: and the LORD my God shall come, and all the saints with thee.
The coming of the Lord with all the saints is the return of Jesus to the earth accompanied by the redeemed and by angels. He descends and stands upon the Mount of Olives. That mount is the place from which He ascended after His resurrection.
This takes place at the close of the thousand years, after the saints have reigned for a thousand years in the Holy City. He descends with the angels and the saints as the wicked dead are raised. Those who held that His descent takes place before the wicked dead are raised and gather around the city placed it before that raising and gathering.
As His feet rest there, the Mount of Olives splits apart to form a great valley and becomes a broad plain. Those who flee are the wicked dead just raised, and those who pierced Him see Him in glory and mourn. The resulting plain is the prepared place where the Paradise of God rests, and the New Jerusalem descends from heaven from God to settle there, with Christ entering the city with His people and the angels. After the wicked surround the city, fire from God destroys them and purifies the sin-cursed earth.