IMO you should just disconnect the battery while doing the Z-tube, only because you are dealing in the Throttle Body and the MAF areas. No need to disconnect either of these guys for the Z-tube install, but it's just good practice to disconnect the battery when working in the engine bay. Bend a wire harness too far and you could damage the electronics in these items with an accidental short. Not a huge risk, but better safe than sorry.
As for resetting the ECU, there are several ways to do it. Disconnecting the battery overnight will definitely work. Also, pump the brake pedal a couple times after you disconnect the battery. This will drain a little extra juice. You'll know your ECU has been reset when you lose all your radio presets, lol. Resetting your ECU only clears the "learned" cells, based on your driving habbits. When adding mods and resetting the ECU, it will take about a tank of gas before the MPGs and trip computers start reflecting the resulting change.
