Possible meaning of "bulls" is 1) soldiers or 2) strong young men. Killing them is spoken of as taking them to a place of slaughter. (See: [[rc://en/ta/man/jit/figs-metaphor]])
Yahweh speaks this to the enemies of Babylon. This can be made clear. Alternate translation: "You enemies of Babylon, kill all her bulls" (See: [[rc://en/ta/man/jit/figs-explicit]])
The phrases "their day" and "the time" mean the same thing and can be combined. Alternate translation: "the time for their punishment has come" (See: [[rc://en/ta/man/jit/figs-doublet]])