Preheat the oven to 450 degrees F. Lay out four 12-inch sheets of heavy-duty foil. Divide the leeks, carrots, chickpeas and olives among the foil sheets and mound in the center; season with salt and pepper. Drizzle with 3 tablespoons olive oil and 2 tablespoons water; top each with a strip of lemon zest. Season the fish with salt and pepper on both sides; place a fillet on top of each vegetable mound. Bring the edges of the foil together and fold to seal, leaving room for steam to circulate.
Transfer the foil packets to a baking sheet and bake until the vegetables are tender and the fish is cooked through, 15 to 20 minutes. Remove from the oven and set aside.
Meanwhile, combine the parsley, mint, lemon juice, coriander, paprika and 1/2 teaspoon each salt and pepper in a food processor or mini chopper; pulse until finely chopped. Add the remaining 1/4 cup olive oil and process until combined.
Divide the foil packets among plates and carefully open. Top with the herb sauce and serve with lemon wedges.