“he hated playing in the studio”
Zappa’s studio was his home. He lived and breathed studio.
Zappa liked his improvisations while playing live. So he constantly recorded multitrack on all his shows.
He was also known to take Solos from song A and apply them to song B. He mixed and mashed live recordings.
Yes, that applied to everything but his lead guitar tracks. And he was a master in the studio, as you know.