A lot of good information here. But I did not see this point: the whole reason for using a zone system is to get a good print on the first exposure in the darkroom. But the first step in developing a zone system for yourself is to determine the density range your enlarhing paper has with a particular developer and time. You then test and test until you figure out what your expsure and development times are with a given film/developer settings to get a N expsure. Then you continue testing for N+1, N+2, etc etc.
Of course after all this testing you may still have to dodge or burn some areas until you get a print you are satisfied with.