double rotationX = Vector3D.AngleBetween(new Vector3D(1, 0, 0), yourMatrix3D.Transform(new Vector3D(1, 0, 0)));
double rotationY = Vector3D.AngleBetween(new Vector3D(0, 1, 0), yourMatrix3D.Transform(new Vector3D(0, 1, 0)));
double rotationZ = Vector3D.AngleBetween(new Vector3D(0, 0, 1), yourMatrix3D.Transform(new Vector3D(0, 0, 1)));
Run Code Online (Sandbox Code Playgroud)