* Glass: The glass (windshield, side, and rear) is *likely* interchangeable between a 1999 Jeep Cherokee (XJ) and a 1996 Jeep Grand Cherokee (ZJ). However, you should verify part numbers to be absolutely certain. While body styles differ, the glass dimensions might be similar enough for some parts, but not necessarily all.
* Drivetrain: This is where it gets much more complicated and the answer is largely no. While both used variations of the AMC/Jeep 4.0L inline-6 engine, the transmissions and transfer cases were different between the XJ Cherokee and the ZJ Grand Cherokee, especially across the model years you specified. Even if the engine itself *might* be swappable (with considerable work), the rest of the drivetrain components (transmission, transfer case, axles, driveshafts) are almost certainly *not* directly interchangeable.
In short: Always verify part numbers before purchasing any parts to guarantee compatibility. Using a reliable parts database or contacting a Jeep parts specialist is highly recommended to avoid costly mistakes. The chances of glass interchangeability are higher than drivetrain parts.
