If you really want a system that will allow you to get some control with 35 mm I would recommend you forget the ZS and try the BTZS. Phil even has a section in his book for roll film users. Of course, as with the ZS the BTZS is optimized for use with single sheet, but, and here is the big but, it allows a better exposure control than the ZS. Since the incident metering systems relies on the measurement of the shadows as the recomended exposure, you will always have an apropriate exposure regardless of the development done, you can then use paper grades instead of the N+ or N- development times.
I ahve used both, and was a long time ZS user, and I have to say the BTZS is a far better option even for roll film users.