Let's consider two different types of mourning.

And I will pour on the house of David and on the inhabitants of Jerusalem the Spirit of grace and supplication; then they will look on Me whom they pierced. Yes, they will mourn for Him as one mourns for his only son, and grieve for Him as one grieves for a firstborn.  In that day there shall be a great mourning in Jerusalem, like the mourning at Hadad Rimmon in the plain of Megiddo. And the land shall mourn, every family by itself: the family of the house of David by itself, and their wives by themselves; the family of the house of Nathan by itself, and their wives by themselves; the family of the house of Levi by itself, and their wives by themselves; the family of Shimei by itself, and their wives by themselves;  all the families that remain, every family by itself, and their wives by themselves.

Here we see an isolated form of mourning, but to see the other, let's read Revelation 1: 4-7

John, to the seven churches which are in Asia:

Grace to you and peace from Him who is and who was and who is to come, and from the seven Spirits who are before His throne,  and from Jesus Christ, the faithful witness, the firstborn from the dead, and the ruler over the kings of the earth.

To Him who loved us and washed us from our sins in His own blood, and has made us kings and priests to His God and Father, to Him be glory and dominion forever and ever. Amen.

 Behold, He is coming with clouds, and every eye will see Him, even they who pierced Him. And all the tribes of the earth will mourn because of Him. Even so, Amen.

So we see 2 types of mourning. Those in their own homes, and those on the day when Jesus comes again.

Now as in Zachariah, all families mourned in their own homes implying that their mourning was isolated, so too was ours before we became Christians. We mourn our sinful spiritual state which leads us to desire to be baptized- washed from our sins as found in Revelation 1 verses 5 and 6.

But for those who do not, for those who neglect Christ's sacrifice they will be as those in verse 7.

In conclusion, this chapter of Zachariah we see all mourn, but independently. So is our mourning. All shall mourn, but we do so separately. This means that we all must decide for ourselves which form of mourning we desire.