I think I’ve answered my own question. First of all, I can select between the various versions by reading from one of the vanguard.zi, rearguard.zi, or main.zi files. (I had been reading all of the files like africa, europe, northamerica, etc., separately at first.) Then whatever I want or don’t want to use is already commented out or uncommented as needed. Secondly, even if I’m reading those other files rather than the .zi files, I gather that, in my Europe/Dublin example, the vanguard and main data are the same, but if rearguard and main had been the same, it would be the vanguard section that was commented out, and the rearguard section would have been uncommented. I take it from this that, for any given vanguard/rearguard section, you can’t have all three formats defined differently, but rather “main” will either be identical to one of vanguard or rearguard.