This is a reference to this:
Rev 20:9 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.
Only the Father is in heaven at that time so this is not the second coming and not Jesus using the fire.
If it is referring to that, and it indeed may be, that logically places the thousand years before the 2nd coming in that case. Why? Verse 2 in Zechariah 14 happens in this age prior to the 2nd coming. Those in verse 12 that this plague happens to, are meaning the ones in verse 2 who are gathered against Jerusalem, obviously.
Zechariah 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.
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.
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.
19 This shall be the punishment of Egypt, and the punishment of all nations that come not up to keep the feast of tabernacles.
This is meaning after verse 2 and 12 are fulfilled. The text indicates---that every one that is left of all the nations which came against Jerusalem. Obviously that means some survived to live another day, of the nations which came against Jerusalem in verse 2, and some didn't. As to the ones that didn't, what became of them according to the text in Zechariah 14? How can it not be the following?
Zechariah 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.
The text says----And this shall be the plague wherewith the LORD will smite all the people that have fought against Jerusalem.
Zechariah 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.
Has anyone in this verse fought against Jerusalem? Apparently so, therefore verse 12 is being applied to some of these in verse 2 of the nations that come against Jerusalem. And if verse 2 is fulfilled in the end of this present age, then so must the same be true for verse 12. And if verse 12 is meaning Revelation 20:9, there is then no logical way to place the thousand years after the 2nd coming, but that the thousand years must precede the 2nd coming in order for Zechariah 14:12 to not contradict Revelation 20:9, assuming they are both referring to the same event.