if not, i think tiemann beat you by a bit there, though i agree that zortech was more influential throughout the 80s and 90s
https://gcc.gnu.org/releases.html says the first version of gcc to include g++ was 1.15.3 on 01987-12-18. unfortunately it doesn't seem to be preserved in https://ftp.gnu.org/old-gnu/gcc/ where the oldest version present is gcc 1.23 from 01988-06-26; possibly there's a comp.sources archive or something?