I feel your pain! My listening room has 2 4x10 floor to ceiling windows, hardwood floors, and a stone wall at one end. It was bright. 1st reflection is the stone wall on one side, then an open doorway on the other side.
1. rugs, blankets over furniture.
2. window treatments, fabric blinds works well, but you get no light (also affects plants) added blackout curtains (they are super heavy, made to absorb sound) also added shear coverings over the entire window.
3. Fabric wall hangings. Have a few canvas pictures up, packed the backs with rock wool. There are 2 just behind each speaker. Along the long walls to my listening position.
4. big plants. Have huge fern, a palm, other plants, they really do make a difference, and warm up the room.
5. Weirdly, my record collection along the wall, helped calm the room down.
6. Added L-Pads to my tweeters. Not sure this is really a thing, as they are replacement tweeters that are +6db louder, kind of needed to be done.
I'm very interested in the ZW-damping disk. What are they made from? Are they just Sorbothane disk? Windows absorb resonate and reflect so much sound!