Which of the Jerusalems found below are you talking about?
Gal 4:25 For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children.
Gal 4:26 But Jerusalem which is above is free, which is the mother of us all.
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Let's assume it's meaning the one in verse 26.
Zechariah 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.
That would indicate that we have to apply Jerusalem in the same manner here as well. We then end up with the text basically saying----All the land shall be turned as a plain from Geba to Rimmon south of Jerusalem which is above is free, which is the mother of us all.
I had no clue though, that there could even be the south of something that is not even literal. But if we make Jerusalem a literal place geographically located, then compass directions, such as south, tend to make sense, in regards to it.
Zechariah 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 is meaning the very same Jerusalem in verse 2. Should this be understood like such---And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem which is above is free, which is the mother of us all, on the east?
I just can't see Jerusalem in Zechariah 14 fitting any other sense than a literal city. Because IMO, if what one takes something to mean, and if they insert that meaning into the text, like I did above, and that it results in nonsense rather than perfect sense, that's a pretty good indication that that one might need to chunk that interpretation and try one that doesn't make nonsense of any of the texts involved.