Meanwhile make lemon in herb sauce: In a blender combine 2 cloves garlic, parsley, cilantro, dill, scallion, lemon zest, lemon juice, 1/4 teaspoon salt and 1/4 teaspoon black pepper and blend until combined. Set aside.
Remove sheet pan from oven and add sliced zucchini with green bean mixture and combine. Clear space in the middle of the sheet pan to add the fish. Place fish on sheet pan and lightly drizzle with remaining 2 teaspoons oil, 3/4 teaspoon salt and 1/2 teaspoon black pepper. Return to oven and continue to bake for 15-17 minutes, or until the fish is just cooked through. (See note)
Drizzle cooked fish and vegetables with lemon herb sauce and garnish with lemon slices!
You can tell a fish is cooked through by sticking a thin knife in the center. The fish is fully cooked when there is no resistance when inserting the knife or the fish reaches a temperature of 145ºF in the center.