Blessed Relief is the closest Frank got to being more jazz than Zappa, if you know what I mean. All of The Grand Wazoo and Wazoo is he most jazz Frank ever got.
I enjoy all the ones already mentioned, but can we talk about Big Swifty and King Kong on MAJNH. That's one of my go-to's when craving some jazzier Zappa.
Frank definitely was inspired by jazz, or jazzy things. You can hear at least a little bit of jazz, whether in chords or phrasing, etc. in almost every Zappa album. All those albums with Tommy Mars and other late-70s/80s albums, there is fusion/jazz all over the place, sometimes obvious, sometimes not.
Gail Zappa, zappa.com, December 2, 2010
Dance Me This?—2011
Gail Zappa, zappa.com, November 2010
Dance Me This and The Rage And The Fury should be out by 2012.
Gail Zappa, zappa.com, March 28, 2012
Within the year from now.