en_tn/isa/27/13.md

a great trumpet will be blown

This can be stated in active form. Alternate translation: "someone will blow a trumpet loudly" (See: rc://en/ta/man/translate/figs-activepassive)

will come

"will return to Jerusalem"

and the outcasts in the land of Egypt

The verb "will come" is understood from the previous clause. Alternate translation: "the outcasts in the land of Egypt will come" (See: rc://en/ta/man/translate/figs-ellipsis)

holy mountain

The "holy mountain" is Mount Zion, in Jerusalem. See how you translated this in Isaiah 11:9.