en_tn_lite_do_not_use/zec/02/05.md

I ... will become for her a wall of fire around her

People built walls around their cities for protection. Here Yahweh speaks of protecting Jerusalem as if he himself were a wall of fire around the city. Alternate translation: "I ... will protect the city, like a wall of fire around it" (See: rc://en/ta/man/jit/figs-metaphor)

this is Yahweh's declaration

Yahweh speaks of himself by name to express the certainty of what he is declaring. See how you translated this in Zechariah 1:4. Alternate translation: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: rc://en/ta/man/jit/figs-123person)