Zec 12:9 And it shall come to pass in that day, that I will seek to destroy all the nations that come against Jerusalem.
all the nations that do come against spiritual Jerusalem ( the Church ) will be destroyed on the last day, when Jesus comes again in judgement. this IN NO WAY is talking about the physical city in the middle east called Jerusalem, which is a type of the heavenly Jerusalem.
NO WAY. He is talking directly to Judah.