Make the Marinade: In a small bowl, whisk together olive oil, lemon zest and juice, garlic, parsley, mint, oregano, smoked paprika, sumac, red pepper flakes, and salt. Reserve 3 tablespoons in a separate small container for finishing.
Prep Components: Cut vegetables uniformly. Pat shrimp very dry with paper towels.
Marinate: Add bell peppers, zucchini, and red onion to a large mixing bowl; toss with the main portion of the marinade and rest 10 minutes. Add shrimp; toss to coat and marinate 10–15 minutes more (do not exceed this time).
Assemble Skewers: Thread shrimp and vegetables alternately, leaving slight gaps for airflow. Aim for about 4 shrimp per skewer.
Grill: Preheat grill to medium-high (400–450°F / 200–230°C). Oil grates. Grill skewers ~3–4 minutes per side until shrimp are pink and opaque and vegetables are tender-crisp with light char.
Finish: Transfer to a platter and immediately drizzle with the reserved fresh marinade. Discard any marinade remaining in the mixing bowl. Serve at once.