Here's a link to some basic information about a code zero. CRUISING CODE ZERO FAQ - Ullman Sails
IMO, before you seriously consider buying a sail with a limited range of use, you should first learn how to get the most performance out of the sails you have.
Sailing in light air requires powering up the sails, keeping them full and reducing drag.
You power up the sails by easing all the controls, including the main and jib halyards and the mainsail outhaul to give the sails a powerful, deep draft.
You keep the sails full by moving your crew weight to leeward, to force the boat to heel. Gravity will then cause the sails to hang in that curved shape that drives the boat.
Finally, you reduce drag by moving your crew weight forward, near the mast stays. That will force the bow down and raise the stern slightly, lifting part of the stern out of the water. That reduces wetted surface, which reduces drag.
In light air, you have so little air movement to work with, that you have to do all three of these things to maximize the boat's performance. Most racers do one or two, but not many do all three.