From someone who is not familiar with Zappa work. I do have a question and I ask this out if curiosity and not with snarkiness.

So what exactly are the innovations of Frank Zappa concert works that would make his work still be studied in 100 years?

I mean Greenberg did an entire lecture series on 20th century music and not once mentioned Frank Zappa. I’m sure there’s a good reason he finds him a worthy composer perhaps due to good compositional technique. However that statement of still being studied/remember hundred years from now implies some sort of innovation that makes his composition essential for future composers to learn about.

Just from reading your reviews he just seems to be one of many composers using modern compositional technique (I assume either from free atonality, polytonality or serialism)