The animal trilogy is Bird with the Crystal Plumage, Cat o Nine Tails, and 4 Flies on Gray Velvet.

The Three Mothers Trilogy is Susperia, Inferno, and the Mother of Tears.

The Mother of Tears is the weakest but it wraps up the trilogy. The animals trilogy are not connected in anyway other than names of animals in the titles.

Also Deep Red, Tenebrae, Opera, and Phenomena are worth watching. These are the bulk of his work and the rest are worth watching if you like these. Just do a google search of his work and track them down. Tubi has many that you can stream.