Preheat Oven: Preheat the oven to 400°F so it’s ready when your foil packets are assembled.
Mix Vegetables: In a large bowl, combine the sliced zucchini, corn kernels, sliced shiitake mushrooms, sliced shallots, and sliced red bell pepper.
Season Vegetables: Add 2 tablespoons chopped cilantro, ½ teaspoon salt, and ¼ teaspoon black pepper to the vegetables, then toss until everything is evenly coated.
Make Curry Sauce: In a second bowl, whisk together the green curry paste, minced garlic, remaining 2 tablespoons chopped cilantro, lime zest, coconut milk, remaining ½ teaspoon salt, and remaining ¼ teaspoon black pepper until smooth.
Build Foil Packets: Lay out 2 large sheets of aluminum foil on a baking sheet. Divide the vegetable mixture between the centers of the foil sheets.
Add Fish: Place one fish fillet on top of each pile of vegetables.
Sauce and Seal: Spoon the coconut curry sauce over the fish and vegetables. Fold the foil over the food and crimp the edges tightly to seal each packet.
Bake Packets: Bake for about 15 minutes, or until the fish is opaque and flakes easily with a fork.
Serve Carefully: Open packets carefully to avoid steam burns, then serve the fish and vegetables straight from the foil or transfer to plates.