The Zeiss lenses aren't really known for their close-focusing abilties. Extension rings (extortionately expensive for what they are) is what you need. Although, it helps to have a longer focal length to start with. I use a 32mm ring on a 150mm Sonnar. On the 80mm, it gets you really really really close. You might consider swapping the 80mm for the 120mm macro.
Somebody here has the formulas for calculating magnification, distance, extension, light loss... can't seem to find them now.