I'm just talking about what people are trying to do when they run ZS EI tests, and what is at stake in terms of image quality etc when one chooses a different EI than the ISO speed. ZS testers are trying to find an effective film speed such that given their processing procedures, when they meter and close down two stops for shadows, they get full separations in the negative. So I don't understand how it is a question of film speed at all. ZS tests are just exposure/development tests to get a desired tonality. Whether or not they get what they think they are getting is another matter.