The main ingredient in Windex is ammonia & yes a lot of window washing fluids have that in them as well as alcohol. Yes it likewise WILL clean muzzleloaders but be mindful of such rust & corrosive solvents & keep the then bared steel oiled!
Brake cleaner is what I use & prefer for quick mzldr clean ups. Just be sure & try to keep it off (or wipe off quickly if you get some on it) plastic stocks & other plastic pieces like say cleaning rod ends & sabots! Again, it will also strip the steel to bare metal so put oil or your favorite preservative fluid back on the metal before storing it.