Yahweh telling the people of Jerusalem to rejoice because there will be many people living in Jerusalem again is spoken of as if Yahweh were telling a barren women she is going to have many children. (See: [[rc://en/ta/man/translate/figs-metaphor]])
# break into joyful singing and cry aloud, you who have never been in birth labor
This statement means the same thing as the first part of the sentence. (See: [[rc://en/ta/man/translate/figs-parallelism]])
An event that will happen in the future is spoken of as if it happened in the past. This emphasizes that the event will certainly happen. Alternate translation: "For the children of the desolate woman will be more" (See: [[rc://en/ta/man/translate/figs-pastforfuture]])