Hip Internal Rotation Sequence
Going through this sequence improved my hip IR by about 25 degrees.
I honestly feel like a happy obturator nerve and some focused medial hip glides really work the magic here.
My next suggestion would be to break down teaching pelvic on femur hip rotational movement patterns. (I have an old video for that here on IG- #movementrevhips)
However these 3 things and cleaning up the Z-sit in part 1 of this question are great tools to have.