I put a set of LED headlight bulbs in my Mazda 3 DD. One of the issues with the LED bulbs is that there is a fan attached to the back of the bulbs. On cars I have owned in the past, there is usually a round plastic cover that you need to take off, and then you can remove the lightbulb. I didn't realize about the fan on the back of the bulbs, but luckily on the Mazda, there is no plastic cover (the bulb has a rubber O-ring gasket to seal it from the elements). I haven't checked if there is even room to install these in the Z, but chances are if there is a plastic cover, this will have to be left off, and then there is no protection from the elements for the bulb and headlight.
As far as light output, if you look at LED bulbs, there is only one LED bulb on the headlight. There really needs to be two (one on each side). As others have mentioned, LED projectors from the factory are specifically designed for LEDs, whereas our HID projectors are not. When the bulb is on, there is more light output in front of the car, but less as the distance increases. I think when there is finally a bulb that has a LED on each side, it might be a lot better. Just my
