Alex,
Welcome to BladeForums, and the Busse forum in particular! The regular BM-E weighs 21 oz. according to the page from the old Busse website. With the thickness of the steel on the BM-E = 1/4", and the ZTBM = 3/16", I would guess the weight of the ZTBM steel to be roughly 75% of the BM-E. The weight of the micarta would be the same on both models, and the slightly different grinds would have some influence on the difference in weight, so as a guess using 80% x 21 oz. = 17 oz. for the ZTBM. I have a SH-E and a ZTSH, and the difference in weight is readily noticeable, and would be even more noticeable in the longer Battle Mistress.
Nearly all of the Zero Tolerance models were uncoated, but there were a relative few that had the black crinkle coat. Even the coated ZT models have the swedge grind at the top by the tip, so this is how you can tell a coated ZT model from the regular Ergo model. The swedge grind would make the blade from a side view look like somewhat of a spear point, although the grind is not deep enough to give it a false edge (it is flat on top of the swedge grind). Also, "Ergo" refers to the handle shape, which is the same on both the ZTBM and BM-E; in other words, the ZT models are a type of Ergo model, although they are usually not referred to as an Ergo model but just as a Zero Tolerance model.
Gene