Melt the butter in a large shallow pan. Add the carrots and fennel and saute gently for 3 minutes. Stir in the zucchini, lemon rind and parsley.
Arrange the fish steaks on top of the vegetables, season with salt and pepper and pour on the wine. Cover tightly and simmer for about 10-12 minutes until the fish is opaque and cooked through.
Carefully lift the fish steaks onto a warmed serving plated and surround with vegetables. Spoon the juices over the fish and garnish with lemon and parsley.