You should seek out the documentary film "From Straight to Bizarre". It covers the Hurvitz LP and Zappa's brief role. Their creative falling out is talked about in depth. Seems that Zappa was interested in spending more time on things like the Wild Man Fisher album, and after an argument in the studio about production style, Zappa avoided the Hurvitz sessions all together. I believe it was Ian Underwood that was assigned to (under)produce and complete the album with Sandy. Hurvitz never was very happy with how the finished album turned out in it's lackluster form.
Have you seen "Essra Mohawk (aka: Sandy Hurvitz) Talks of Frank Zappa" on Youtube? > http://youtu.be/cWCdlrAVqTU