Let me put it this way then. If Zechariah 14:16-19 wasn't even meaning post the 2nd coming, problem would be solved in that case. But if it is meaning post the 2nd coming, then there is a problem with your interpretation and not mine. You're the one that needs to explain how Jesus can destroy all of the unsaved at His coming, leaving nothing but immortal saints, then there still being these unsaved survivors in Zechariah 14:16-19 post the 2nd coming. Where I come from that sounds like a contradiction, and not something that is squaring in both testaments.
What did Zechariah see in his vision?
Let us look at it, and compare it to the New Covenant "tabernacle", and "feast".
(Christ) (Lord's Supper)
Zec 14:1 Behold, the day of the LORD cometh, and thy spoil shall be divided in the midst of thee.
Zec 14:2 For I will gather all nations against Jerusalem to battle; and the city shall be taken, and the houses rifled, and the women ravished; and half of the city shall go forth into captivity, and the residue of the people shall not be cut off from the city.
Zec 14:3 Then shall the LORD go forth, and fight against those nations, as when he fought in the day of battle.
Zec 14:4
And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, and there shall be a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south.
(This sounds like the greatest earthquake in history found in Revelation chapter 16. It also moves all of the islands, and destroys all of the mountains, and the cities of the nations fall.)
Zec 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.
Zec 14:6 And it shall come to pass in that day, that the light shall not be clear, nor dark:
Zec 14:7 But it shall be one day which shall be known to the LORD, not day, nor night: but it shall come to pass, that at evening time it shall be light.
Zec 14:8 And it shall be in that day, that
living waters shall go out from Jerusalem; half of them toward the former sea, and half of them toward the hinder sea: in summer and in winter shall it be.
(This sounds like the waters of life found in Revelation 22:1.)
Zec 14:9
And the LORD shall be king over all the earth: in that day shall there be one LORD, and his name one.
Zec 14:10 All the land shall be turned as a plain from Geba to Rimmon south of Jerusalem: and it shall be lifted up, and inhabited in her place, from Benjamin's gate unto the place of the first gate, unto the corner gate, and from the tower of Hananeel unto the king's winepresses.
Zec 14:11
And men shall dwell in it, and there shall be no more utter destruction; but Jerusalem shall be safely inhabited.
(Is this the earthly city of Jerusalem, or the one found above, promised to the Old Testament Saints in Hebrews 11:15-16?)
Zec 14:12 And this shall be
the plague wherewith the LORD will smite all the people that have fought against Jerusalem;
Their flesh shall consume away while they stand upon their feet, and their eyes shall consume away in their holes, and their tongue shall consume away in their mouth.
(This sounds like 2 Thessalonians 1:7-10, when Christ returns "in flaming fire" taking vengeance on those who do not know God.)
Zec 14:13 And it shall come to pass in that day, that a great tumult from the LORD shall be among them; and they shall lay hold every one on the hand of his neighbour, and his hand shall rise up against the hand of his neighbour.
Zec 14:14 And Judah also shall fight at Jerusalem; and the wealth of all the heathen round about shall be gathered together, gold, and silver, and apparel, in great abundance.
Zec 14:15 And so shall be the plague of the horse, of the mule, of the camel, and of the ass, and of all the beasts that shall be in these tents, as this plague.
Zec 14:16
And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the LORD of hosts, and to keep the feast of tabernacles.
(If those who oppose God, and Christ, are destroyed in the battle above, why would anyone think the people in this verse are not believers?)
Zec 14:17 And it shall be, that whoso will not come up of all the families of the earth unto Jerusalem to worship the King, the LORD of hosts, even upon them shall be no rain.
Zec 14:18 And if the family of Egypt go not up, and come not, that have no rain;
there shall be the plague, wherewith the LORD will smite the heathen that come not up to keep the feast of tabernacles.
(This refers back to those earlier in the passage. What happens to those who do not partake of the "feast of tabernacles", which is most likely a reference to the New Covenant, and the Lord's Supper? The plaque is what happens to those people who reject Christ.)
Zec 14:19 This shall be the punishment of Egypt, and the punishment of all nations that come not up to keep the feast of tabernacles.
(These were those who rejected Christ's "feast of tabernacles", and received the plague.)
Zec 14:20 In that day shall there be upon the bells of the horses, HOLINESS UNTO THE LORD; and the pots in the LORD'S house shall be like the bowls before the altar.
Zec 14:21 Yea, every pot in Jerusalem and in Judah shall be holiness unto the LORD of hosts: and all they that sacrifice shall come and take of them, and seethe therein:
and in that day there shall be no more the Canaanite in the house of the LORD of hosts.
(All of the unbelievers were destroyed by the plague earlier in the passage.)
.........................................
Would Zechariah have completely understood the New Covenant, and the Lord's Supper, as we understand it today?
Luk_22:30
That ye may eat and drink at my table in my kingdom, and sit on thrones judging the twelve tribes of Israel.
Joh_6:53 Then Jesus said unto them, Verily, verily, I say unto you,
Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you.
.