Preheat oven to 400°F and line a baking sheet with parchment paper.
Rinse the quinoa under cold water, then combine with 0.5 cup water in a small pot; bring to a boil, reduce to a simmer, cover, and cook for 12-15 minutes.
Pat the cod fillets dry with a paper towel and place them on the prepared baking sheet.
In a small bowl, whisk together half the olive oil, lemon juice, lemon zest, minced parsley, half the salt, and half the pepper.
Brush the lemon-herb mixture generously over the cod fillets.
Roast the cod in the oven for 12-15 minutes until the fish is opaque and flakes easily with a fork.
While the fish roasts, slice the zucchini into half-moons and finely mince the shallot.
Heat the remaining olive oil in a skillet over medium heat; sauté the shallot until translucent, then add zucchini and remaining salt and pepper.
Cook the zucchini for 5-7 minutes until tender-crisp and slightly golden.
Fluff the quinoa with a fork and serve the roasted cod on a bed of quinoa with the sautéed zucchini on the side.