i did exactly what you did and i still i get this error:
/Documents/maya/2017/scripts\zBuilder\nodes\base.py line 72: list indices must be integers, not str #
The first time i did the test i rename everything with the prefix, not only zMaterial, zTissue and zTet
but also, zEmbedder, zGeo even tweak!!
Today i did the test with renaming only zMaterial, zTissue and zTet but nothing happens..
Also one question is it important to create a new sphere or i can duplicate the existing one, mirror, freeze transforms and delete history?
i have send the scene with the ball at your mail
Thank you very much for your help