When he enters your gates, he will enter as men come into a city whose walls have been broken down

Here Yahweh uses a simile to describe how Nebuchadnezzar's army will enter into the city of Tyre. (See: rc://en/ta/man/jit/figs-simile)

whose walls have been broken down

This can be stated in active form. Alternate translation: "after breaking down its walls" (See: rc://en/ta/man/jit/figs-activepassive)