Preheat the oven to 425°F (220°C). Line a large sheet pan with parchment paper or lightly grease it.
In a small bowl, combine the olive oil, minced garlic, dried oregano, dried thyme, smoked paprika, salt, black pepper, lemon zest, and lemon juice. Stir well to create the marinade.
Place the chicken thighs in a large bowl and pour half of the marinade over them. Toss to coat evenly and set aside.
In another bowl, place the shrimp, red bell pepper, yellow bell pepper, zucchini, and red onion. Pour the remaining marinade over the vegetables and shrimp, tossing to coat evenly.
Arrange the chicken thighs on one side of the prepared sheet pan, skin side up. Spread the shrimp and vegetables on the other side in a single layer.
Roast in the preheated oven for 20 minutes.
After 20 minutes, remove the sheet pan from the oven and flip the chicken thighs skin side down. Stir the shrimp and vegetables gently to ensure even cooking.
Return the sheet pan to the oven and roast for an additional 5 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the shrimp are pink and opaque.
Remove from oven and sprinkle the chopped fresh parsley over the chicken, shrimp, and vegetables.
Serve immediately and enjoy your flavorful chicken and shrimp sheet pan meal.