In a mixing bowl, combine olive oil, lemon juice, lime juice, garlic powder, salt, black pepper, and dried oregano. Whisk until well combined.

Add the sliced zucchini, red bell pepper, yellow bell pepper, red onion, and cherry tomatoes to the marinade. Toss to coat and let sit for at least 10 minutes.

Preheat the grill to medium-high heat. Grill the marinated vegetables for about 5-7 minutes on each side, or until tender and slightly charred.

In serving bowls, layer the grilled vegetables, sliced avocado, crumbled feta cheese, and chopped cilantro. Drizzle with any remaining marinade if desired.