Triangolo Erotico (1982)
Starring: Mark Shannon, Riccardo Zamagni, Guiseppe Curia, Guia Lauri Filzi, Sabrina Mastrolorenzi, Guiseppe Alotta, Samuel Sandy.
Cathy Menard and Elisabeth Bure clearly feature and Sabrina Mastrolorenzi does not. IMDB also lists Nadine Duenner (Nadine Roussial) who plays the wife and Christina Maffei. Mark Shannon reminisces as he drives along about the love triangle he is involved in. His mistress is Cathy Menard, but she will have sex with anything human including his wife, the maid, another man and groups in what seems to be a dress shop (just a room with a clothes rack and Elisabeth Bure in attendance). Three other women (Guia Lauri Filzi, Pauline Teutscher and one only fleetingly seen) and three other men are involved in the final orgy in which Cathy persuades Mark to participate.
NOTICE: IF THERE ARE LINKS FROM 2 DIFFERENT HOSTS. ONE OF THEM IS MIRROR.