I wrote this in response to another Z owner having problems with his windows. His initial question had been about the need for the pressure roller situated on the top part of the door and it's effect on the window operation.
I also wrote down the steps to adjust a door window to operate smoothly.
The window roller is required to push the glass inward as it reaches the top of it's travel. The inside door panel and the fuzzy strip attached to it, push the window outwards. Between these two and the window frame and front sash the whole thing is maintained in the center of the window frame.
The fuzzy gasket in the top part of your window frame should be FUZZY, no grease, no bare rubber spots. Grease here will just get all over your shirt sleeve. Bare rubber will just prevent the window from rolling up and down smoothly. The inner fuzzy strip mounted to the panel is what presses against the window to push it out, if it's missing or caked solid with dirt / grease / gunk it will just impede the sliding of the pane. The outer gasket on the chrome trim is to seal the window from rain once the window is closed, it is the roller which locates the window in the center of the frame.
That you have to loosen the front sash and the rear guide channel (there is no rear sash) tells me that you don't have these adjusted right, or that your frame is bent or that it's misaligned.
The adjustment for the window is straight forward. You DO have to have the glass bumper roller installed or it will be a b*tch.
1. Loosen the installation nuts for the front sash and rear guide channel.
2. Roll the window up and down and check the alignment of the rear edge of the glass with the door frame.
3. If the glass angles too far to the rear, move the rear guide channel upward. If it angles too far to the front, move it downward. As a general rule, the rear guide channel bolts will both be at the same location within their respective slotted holes to each other, i.e. front bolt won't be higher or lower than the rear bolt in relation to the bolt hole in the metal door frame.
4. When the glass is parallel with the window frame, adjust the front sash so it is parallel with the front edge of the window. You can just look down from above and ensure that the nylon guide mounted on the bottom channel of the window pane is going to go up and down the front sash smoothly.
If your regulator is not allowing you to crank up the window after this, check to make sure that the spring on the regulator isn't broken. Without this spring it is literally impossible to raise the window. The sheer weight of the pane is too much for the angle / gearing in the regulator. The gear within the mechanism will just work its way out of the teeth on the arm. The spring is what helps you counter the weight of the window pane against gravity.