1. In a large nonreactive saucepan, simmer the first 7 ingredients with 6 tablespoons of salt and 1/4 cup of water for 5 minutes. Cover, remove from the heat and let stand for 20 minutes. Add the celery, bell peppers, onions and zucchini.
2. Meanwhile, in each of 2 large skillets, heat 1/4 inch of oil. Season the fish fillets with salt and pepper. Add the fillets in batches, skin side down, and cook over high heat until browned on 1 side, about 8 minutes. Turn the fish and cook until done, about 4 minutes. Reduce the heat if the oil gets too hot.
3. Divide the marinade and the fillets, skin side up, between 2 large deep platters. Scatter the vegetables around the fish. Set aside at room temperature to marinate for at least 1 hour and up to 6 hours. Serve at room temperature.