In a medium bowl, whisk lemon juice, olive oil, salt, thyme, pepper, garlic powder, oregano and rosemary. Add fish fillets and toss to coat. Marinade at least 30 minutes in a sealed plastic bag, up to 1 day.
To cook:
Preheat oven to 400 degrees F.
Toss cherry tomatoes, zucchini and chickpeas onto a large baking sheet. Add olive oil, balsamic vinegar, salt, pepper and garlic powder, tossing to coat. Bake for 10 minutes.
Remove from oven and place fish fillets on pan, surrounded by vegetable mixture. Place 2 lemon slices on top of each fish fillet. Cover with aluminum foil and bake for 10 minutes, until fish is opaque and fully cooked. Garnish with chopped parsley before serving.