RobH_en_tn/ezk/35/15.md

As you rejoiced over the inheritance of the people of Israel because of its desolation

This speaks of the land that Yahweh gave to the Israelites as their inheritance. Alternate translation: "As you rejoiced when I made the land of the Israelites desolate" (See: rc://en/ta/man/translate/figs-metaphor)

I will do the same to you

Possible meanings are 1) I will make your land desolate" or 2) "I will rejoice when your land is desolate" or 3) "I will make other people rejoice because of your desolation."

Then they will know

The word "they" possibly refers to 1) "the people of the earth" or 2) "the people of Israel and Judah."