What most folk forget is that the Zone system is based on visualization or pervisualization (White), it's all about going beyond the record shot and seeing the scene to match the photographers interpretation of the scene to match her/his emotional connection. Minor White lectured that once the shadow is picked (zone II or III in most cases) followed by the highlights the mid zones will just fall into place. If a photogerher picks say zone II for shadow, shadow without much if any detail, and develops for VII the other tones are set as well. So, lets say that the photographer meters the highlight as zone VI but wants to bring into Zone VII, development is +1, that means what was V will be zone VI, zone IV will be zone V, while III and II should not be affected as much. Having taken the Zone workshop from Minor White in the 60s I can say that he was not obsessed with the curve, just understanding how he match a given film and developer to his previsulations. Midtones just follow the highlights.
Without visualization there is really no point to the zone, for a record shot, just a good incident meter, a little testing to adjust ISO for aging shutters and meter, VC paper, and you are good. Or, as I read Phil Davis, for sheet film, BTZS might give really accurate exposures.