Using the Septuagint, it can be seen that the Jerusalem of Zechariah 14:11 is the New Jerusalem.
I agree. The question is, when is verse 11 fulfilled? It can't be fulfilled before verse 2 is fulfilled.
16And it shall come to pass, that whosoever shall be left of all the nations that came against Jerusalem, shall even come up every year to worship the king, the Lord Almighty, and to keep the feast of tabernacles. 17And it shall come to pass, that whosoever of all the families of the earth shall not come up to Jerusalem to worship the king, the Lord Almighty, even these shall be added to the others. 18And if the family of Egypt shall not go up, nor come; then upon them shall be the overthrow with which the Lord shall smite all the nations, whichever of them shall not come up to keep the feast of tabernacles. 19This shall be the sin of Egypt, and the sin of all the nations, whosoever shall not come up to keep the feast of tabernacles.
https://biblehub.com/sep/zechariah/14.htm
What about this part, in relation to verse 11? If verse 11 can't be fulfilled until verse 2 is fulfilled first, then neither can verse 16-19 be fulfilled until verse 2 is fulfilled first.
And it shall come to pass, that whosoever of all the families of the earth shall not come up to Jerusalem to worship the king, the Lord Almighty, even these shall be added to the others.
What happened to the others meant here?
12And this shall be the overthrow with which the Lord will smite all the nations, as many as have fought against Jerusalem; their flesh shall consume away while they are standing upon their feet, and their eyes shall melt out of their holes, and their tongue shall consume away in their mouth.
https://biblehub.com/sep/zechariah/14.htm
We have to keep in mind what verse 16 indicates----And it shall come to pass, that whosoever shall be left of all the nations that came against Jerusalem
When did they come against Jerusalem?
2And I will gather all the Gentiles to Jerusalem to war, and the city shall be taken, and the houses plundered, and the women ravished; and half of the city shall go forth into captivity, but the rest of my people shall not be utterly cut off from the city.
https://biblehub.com/sep/zechariah/14.htm
Apparently then, Jerusalem is come against twice in Zechariah 14. When it is come against the 2nd time around, it is apparently meaning after the thousand years, thus is meaning Revelation 20:7-9.
Revelation 20:7 And when the thousand years are expired, Satan shall be loosed out of his prison,
8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.