Gary,
I put a coat of Z2 on my car today . . . before applying, I filled this small 4 oz. sample bottle (see attached pic) right up to where the "shoulders" of the bottle meet the "neck". The small black dot indicates the level in the bottle after I got done with my WRX. I'd guess that's maybe 1/2 oz., more or less. If you have a full bottle of Z2 (8 oz.), you could use a ruler to measure out 1/2 oz. increments (height of bottle/16); that will give you some feedback as to how much you're applying. In my experience, you will need about the same amount of Z1, maybe a little more.
Caveat: I use a foam polishing pad on a PC 7424 random orbit polisher to apply Z1, and a foam applicator to apply Z2/Z5. I've found this combination allows me to apply very thin coats, and use less product (ymmv, but I've found that terry covered applicators use up more product, and don't "glide" on quite as well).
Hope this helps,
Tort
P.S. I'm going to try to put another coat on tomorrow . . . I'll takes some pics of the foam applicator I use with some product on it, and show just about how much I'm using per panel.