How to Make It
Preheat grill to medium-high heat.
Coat grill rack with cooking spray. Sprinkle fillets with 1/4 teaspoon salt and 1/4 teaspoon pepper; rub fillets evenly with brown sugar. Let stand 5 minutes. Arrange fillets, skin side up, on grill; grill 3 minutes on each side.
Shave zucchini into ribbons using a vegetable peeler. Combine remaining 1/2 teaspoon salt, remaining 3/8 teaspoon pepper, zucchini, fennel, dill, orange rind, and juices; toss. Place about 1 cup zucchini mixture in each of 4 bowls; top each serving with 1 fillet.