Preheat the oven to 400°F. Line a large baking sheet with parchment paper.
In a mixing bowl, combine the panko breadcrumbs, parsley, thyme, lemon zest, minced garlic, 1 tablespoon olive oil, salt, and pepper. Stir until the mixture is evenly moistened.
Pat the cod fillets dry and place them on one half of the prepared baking sheet. Press the herb crust mixture firmly onto the top of each fillet.
Toss the Brussels sprouts with the remaining 2 tablespoons olive oil, lemon juice, and a light sprinkle of salt and pepper. Spread them on the other half of the baking sheet in a single layer.
Bake for 18 to 22 minutes until the cod reaches an internal temperature of 145°F and the crust is golden. The Brussels sprouts should be tender with some browned edges.