The Zone is interesting in that it is as many carbs as you will likely ever need and a starting point for your protein and fat needs. Given your activity level I would put you at about a 0.80-0.85 activity multiplier. Crunch those numbers and lets see what you get for your daily carb allotment. You might try partitioning most of your carbs to post workout times and use sweet potatoes or yams.
Now as to the pre-fight meal, make it relatively small and of a composition that you know you digest well. No surprises on game day! You likely have a few foods that you know you digest well and feel good on a few hours later…that’s what you want. Practice that scenario by eating that meal and then sparring hard a few hours later (try to emulate your fight timing with regards to weigh-ins and schedule leading up to the fight). This will give you and idea of how your stomach empties etc. Keep in mind that come fight day you will likely have some jitters and this can affect gastric emptying.