Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the zucchini into half-moons and toss on the baking sheet with 0.5 tbsp of olive oil, 0.25 tsp sea salt, and the dried oregano.
Roast the zucchini for 15-18 minutes until tender and slightly browned around the edges.
Pat the branzino fillets very dry with paper towels, then season the flesh side with the remaining 0.25 tsp sea salt, black pepper, and garlic powder.
Heat the remaining 1 tbsp of olive oil in a large non-stick skillet over medium-high heat until shimmering.
Place the fish skin-side down in the pan and press gently with a spatula for 30 seconds to ensure even contact for a golden crust.
Cook for 3-4 minutes until the skin is golden, then carefully flip and cook for another 1-2 minutes until opaque throughout.
Remove from heat and immediately top with fresh lemon zest, a squeeze of lemon juice, and chopped parsley before serving with the roasted zucchini.