I finally made it to Yellow Shark.
I was not terribly impressed by it. There is a famous story about the Argentinian composer, Astor Piazzolla, that illustrates my feelings about Zappa's classical works.
Piazzolla played in a tango band, but also wanted to be a composer. The most influential composer of his youth was Stravinsky and he wrote many pieces influenced by the works of Stravinsky. At some point he went to study with Nadia Boulanger, the most famous music teacher of that time. She looked at his Stravinsky inspired works and found them pretty dull. He eventually told her about his tango band and she asked him to play her some of that music. Upon hearing his original tango music, she told him that this is where his genius lies and that this should be his focus.
I think that Zappa's classical music is similar. Without his interest in classical music, he would not have made all of the awesome rock music that he did. However, his genius did not lie in classical music, it was in rock music and that is where his focus should have remained.
I find the end of his discography to be fairly boring. It contains many live albums, classical albums, and "experimental" albums. I much prefer the more straightforward rock albums.
also, the music of Piazzolla is work checking out
https://www.youtube.com/watch?v=1kev-9fYi5Q