This verse constitutes a summary restatement of the content of verses 17-18.

This shall be the punishment to Egypt and the punishment to all the nations: This refers backwards to the whole of verses 17-18. The mention of Egypt and all the nations in parallel seems to emphasize that all who fail to worship the LORD in the Festival of Shelters will suffer a similar fate. The word translated punishment is not the same as the word translated “plague” in the earlier verses. Here it is a word that often means “sin,” as in 13.1, but it is also extended to include the consequence of sin, that is punishment. Punishment to is curious English, and is replaced in New Revised Standard Version by the more natural “punishment of.” In some languages it will be more natural to say “This is the way the LORD will punish the people of Egypt and the people of all the nations.”

That do not go up to keep the feast of booths: See the notes on verse 16.

Quoted with permission from Clark, David J. & Hatton, Howard A. A Handbook on Zechariah. (UBS Helps for Translators). New York: UBS, 2002. For this and other handbooks for translators see here .