Crispin wrote the Sarek novel, but I haven't read that one yet. I think it was a book that came later, after continuity between books was being clamped down on by Richard Arnold, however this is a speculative statement on my part. Having not read it, I can't really make any guesses about references to Zar, though. Maybe Crispin and others were able to sneak things past the editors and censors. I'm only at the beginning of reading through 80's novels, after which I plan to read other books after that loose "continuity" was killed, at which point I will be able to see for myself if the authors were successful in slipping references under the radar.