the ZD8000, I have one of those (it's sitting in my storage area) They are a laptop, which makes them very difficult to swap CPUs. The ZD8000 is even more of a beast, especially since you have to start disassembling from the keyboard down, then flip it over and finish on the back side. In order to even get anywhere inside the thing you have to practically disassemble the entire computer. The easier way I found to reduce the heat around the touchpad (which is where you probably run into the uncomfortableness) is to remove the battery and run straight off the wall plug.
the battery basically stores heat and dissipates it up through the wrist rest area around the trackpad since it's directly above the battery housing.
btw be on the look out for graphics card anomalies, that's why I stopped using mine was because the graphics card failed and in order to replace it, you have to buy a new logic board, which was more than what I initially paid for the machine.