The zinc plating prevents rust on all of the areas NOT swept by the pads. This means the sides of the rotor, the slots/holes, the vanes, and most importantly the "hats".
It also makes wheel and rotor removal much easier, as the rotors will no longer "stick" to the wheels.
Other than the plating, everything else (pads, fluid, lines) can stay just like stock. A slightly more agressive pad will wear through the plating faster (not a bad thing).