Are the windows in an area where smoke, either from cigarettes or
cooking or possibly even from a garage?
If so, you may want to give them a light washdown with alcohol first.
Even 71% Isopropyl will do the trick quickly but I prefer the 91%,
then was them with window cleaner.
I used to own a restaurant eons ago, and the only thing that would
remove the film that builds up on the windows, especially on the sunny
side of the building was alcohol.
Except for the glass on the windows in the fireplace in the lounge.
For those windows we used a very dilute solution of Muriatic Acid to
cut the soot that would stick to them. This also works great on glass
front wood stoves also!