How to Make It
Bring a saucepan of water to a boil. Score an "X" in the bottom of each tomato and blanch them in the boiling water for 30 seconds. Drain and cool the tomatoes under cold running water. Peel, seed and cut the tomatoes into 1/4-inch dice; transfer to a medium bowl.
In a small skillet, heat 2 tablespoons of the olive oil. Add the zucchini and cook over moderate heat, stirring occasionally, until just tender, 3 to 4 minutes. Add the zucchini to the tomatoes. Stir in the lemon zest, lemon juice and sherry vinegar and season with salt. Mix gently and keep warm.
In a large, heavy saucepan, heat the remaining 2 cups of olive oil over moderate heat to 180°. Season the hake with salt and poach in the olive oil until just white throughout, 10 to 12 minutes. Remove the fish with a slotted spatula and drain briefly on paper towels. Season with salt. Spoon the zucchini mixture into shallow bowls, set the fish on top and serve.