Zechariah 14:1-2  “…the day of the LORD is coming…I will gather all the nations to battle against Jerusalem…”
This would make it the end of the Tribulation week just before Christ returns to earth.

2  “…Half of the city shall go into captivity…the remnant of the people shall not be cut off…”
Not like the Babylonian exile, but that half of the city will fall to the invaders before Christ returns.  The believing remnant will be left and rescued by Christ’s return.

4  “…in that day His feet will stand on the Mount of Olives…”
The return of Christ to the Mount of Olives from which He ascended.

4-5  “…Mount of Olives shall be split in two…you shall flee through My mountain valley…the LORD my God will come, And all the saints with You”
Mount of Olives will split along an east/west line.  Half will move north, half will move south creating a valley to the east of Jerusalem.  The remnant will escape the city through that valley, and Christ will go to war against the invading armies of the Antichrist surrounding Jerusalem.  Won’t be much of one.  All He’ll have to do is speak the word and they’ll be destroyed.  Revelation 19.

5  “…the mountain valley shall reach to Azal…”
Tried to find Azal.  They don’t really know.  There is an area southeast of Jerusalem and south of the Mount of Olives which appears to have that name.  But, to me, that doesn’t work out if the Mount splits and moves north and south.  That would put the eastern end of the new valley too far east.  At any rate, it will make sense when it happens.  Interesting note.  There is apparently a fault line running through that area which has been discovered in our time.  Certainly Christ could cause an earthquake and movement anywhere He chose, but the fact that there is already a fault there shows again how God uses what He has already created.  He has set the stage for His return.  All that is needed is His foot to touch the Mount to set off the split.

NOTE:  Just realized I probably misinterpreted the text.  I read it as though the valley reaches to the east to Azal.  But it more likely is saying that the west end of the valley will reach all the way to Azal, which is near the eastern side of Jerusalem, which will allow the people in the city to escape out of it.  The Mount will split and that split will reach all the way to the city.  Where the valley ends up isn’t mentioned, but it obviously leads to a place of safety east of the Mount.

6-7  “…in that day That there will be no light…But at evening time it shall happen That it will be light”
Not sure here.  Commentaries aren’t clear either.  Some suggest more of a spiritual meaning between the light and darkness, but they aren’t specific enough.  Just reading it, it sounds like the natural lights are put out, but that there is light that appears.  Perhaps a light like that at twilight.  Also, the phrase in that day could be referring to in that time or during that time, so it may not be talking about a specific point in time when this happens.  Could be referring to the time of the Millennial Reign.

8-9  “…in that day it shall be That living waters shall flow from Jerusalem, Half of them toward the eastern sea And half of them toward the western sea…the LORD shall be King over all the earth…”
Would definitely be during the time of the Millennial Reign.  Living waters flowing out of Jerusalem while Christ sits enthroned there.  And He is Lord over all the earth.

12  “…Their flesh shall dissolve while they stand on their feet, Their eyes shall dissolve in their sockets, And their tongues shall dissolve in their mouths”
Many today believe this describes a nuclear bomb blast.  Similar description, but Jesus won’t need it.  It says that His enemies are destroyed by the sword which proceeds out of His mouth.  All He will need to do is speak the word, and they’ll be destroyed.  This is apparently how that will happen.  No mention of how long this takes.  Could be in an instance, but could also take some time, like days or weeks.  The fact that it is called a plague hints in that direction.  Not a nice picture.

16  “…everyone who is left of all the nations which came against Jerusalem shall go up from year to year to worship the King, the LORD of hosts, and to keep the Feast of Tabernacles”
All the nations will come to Jerusalem to worship Jesus.  What is said about every knee bowing and every tongue confessing will come true.  The land becoming a plain around Jerusalem will make that easier.  The idea of the Feast of Tabernacles has always confused me as I couldn’t see the need at this point.  From some reading on the subject, it appears that part of the reason for the feast was to point into the future when all the nations would come to Jerusalem to worship the Messiah.  So, when this occurs, the people won’t be coming to celebrate the feast, but the fact that they are coming will be the feast.  All the nations coming to worship Christ in Jerusalem will be the fulfillment of the Feast of Tabernacles.

20-21  Everything is dedicated to Christ.  He is Lord of all, and all is now His.  No more secular and religious.  Christ has made all one as it was supposed to be from the beginning.

I hope you enjoy reading and studying His word.  May it accomplish what He desires.  Please feel free to comment or post questions.  Thanks for reading!

Scripture taken from the New King James Version®. Copyright © 1982 by Thomas Nelson. Used by permission. All rights reserved.