Shoot Fast, Shoot A Lot and Move
If you’re engaging a target from inside a vehicle, odds are you’re reacting to a close quarter threat and time is not on your side. Understand that bullet trajectory is affected by several variables including glass types, glass angles, and even the performance of what ammo you carry, but again, time is NOT on your side so keep it simple.
Whatever window or glass barrier you’re shooting through, SHOOT FAST, SHOOT A LOT AND MOVE! Although the trajectory of the initial rounds will be affected by the glass, they can still be effective rounds on target at close distance while at the same time porting the window to allow the additional rounds to perform as advertised. Shoot as fast as you can shoot accurately, and then move fast and aggressively. Don’t assess your work from your initial position.
Most importantly, train for all these variables. The defensive plan in your head isn’t going to happen, be prepared for things to be as bad as can be.