Yahweh speaks of himself by name to express the certainty of what he is declaring. Alternate translation: "this is what the Lord Yahweh of hosts, the Mighty One of Israel, has declared" or "this is what I, Yahweh, the Mighty One of Israel, have declared" (See: [[rc://en/ta/man/jit/figs-123person]])
Both of these phrases mean basically the same thing. The words "take vengeance against my adversaries" speak more of Yahweh doing whatever he needs to do to those who work against him so he can be happy. The words "avenge myself against my enemies" speak more of Yahweh justly punishing his enemies. Alternate translation: "I will punish those who opposed me" or "I will do what pleases me to those who work against me, and I will justly punish my enemies" (See: [[rc://en/ta/man/jit/figs-parallelism]])