How to Make It
In a large saucepan, cover the fish steaks with 8 cups of water and bring just to a boil over moderately high heat. Reduce the heat to low and simmer, skimming a few times, until the fish is just cooked through, about 8 minutes. Transfer to a plate to cool, then discard the skin and bones. Pour the fish broth into a large bowl.
Heat the oil in a large heavy saucepan. Add the celery, onion and green peppers and cook over moderately low heat, stirring, until wilted, about 10 minutes. Add the tomato, scallions and garlic and cook over moderately high heat, stirring, for 2 minutes. Add the fish broth and saffron, season with salt and pepper and bring to a simmer. Add the chiles, thyme, lime zest and allspice and simmer over low heat for 10 minutes.
In a saucepan of boiling water, simmer the banana slices over moderate heat until tender, about 10 minutes. Transfer to a plate. Add the okra to the water and simmer until tender, about 4 minutes. Drain and add to the banana.
Add the zucchini to the stew and simmer until tender, about 4 minutes. Discard the chiles and lime zest. Add the bananas, okra, lime juice and fish and season with salt and pepper. Serve the stew with rice and lime wedges.