Preheat your outdoor grill to medium-high heat (about 400°F). Tear off 4 large sheets of heavy-duty aluminum foil, about 12 inches long each.

In a small bowl, whisk together the olive oil, minced garlic, lemon juice, lemon zest, dried oregano, sea salt, and black pepper. Set aside.

Divide the sliced zucchini, cherry tomatoes, kalamata olives, and red onion evenly among the center of the 4 foil sheets. Place one cod fillet on top of each vegetable mound.

Spoon the garlic-herb marinade generously over each cod fillet and the surrounding vegetables. Bring the long sides of the foil together over the fish and fold down twice to create a seal, leaving a little room for steam. Fold the short ends in tightly to completely enclose the pack.

Place the sealed foil packets directly on the grill grates. Close the lid and cook for 10-12 minutes, depending on the thickness of your fish.

Carefully open one packet (watch out for hot steam!) to check the cod. It should be fully opaque and flake easily with a fork.

Transfer the contents of the foil packs to plates or shallow bowls. Pour any of the leftover juices from the foil right over the top. Garnish with extra fresh lemon wedges if desired.