Preheat the oven to 375°F.
In a mixing bowl, stir together the breadcrumbs, parsley, lemon zest, ½ teaspoon salt, and ¼ teaspoon black pepper.
Place the cod portions on a baking sheet; spread each portion with 1 Tablespoon mayonnaise. Top with the breadcrumbs, packing them down on the portions to coat.
Bake until the fish is firm and starting to flake, about 15 minutes. Remove from the oven.
To serve, divide the cod and lemon wedges between plates. Serve with tartar sauce on the side, if desired.