The eye is a synecdoche for the whole person. AT: "let us gloat over Zion" or "let us enjoy watching the invaders destroy Zion" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
The writer speaks of Yahweh being ready to destroy the nations as if Yahweh were a farmer who has put his bundles of grain on his threshing floor and is now ready to thresh them. (See: [[rc://en/ta/man/translate/figs-simile]])