Prepare Chimichurri Sauce: In a bowl, whisk together olive oil, red wine vinegar, chopped parsley, chopped cilantro, minced garlic, red pepper flakes, salt, and pepper until well combined. Set aside half for serving.
Marinate Chicken: In a separate bowl, combine the chicken cubes with the other half of the chimichurri sauce. Cover and let marinate in the refrigerator for at least 30 minutes (up to 2 hours for a deeper flavor).
Prepare Veggies: Toss the red and yellow bell peppers and zucchini in a drizzle of olive oil, salt, and pepper to season.
Assemble Skewers: Thread the marinated chicken, bell peppers, and zucchini onto the skewers, alternating between ingredients for a colorful presentation.
Preheat Grill: Heat a grill or grill pan over medium-high heat until hot.
Grill Skewers: Place the skewers on the grill, cooking for about 10-15 minutes, turning occasionally, until the chicken is cooked through and the veggies are slightly charred. Cook until the chicken reaches an internal temperature of 165°F (75°C).
Serve: Arrange the skewers on a serving platter, drizzling with the reserved chimichurri sauce.
Notes
For a deeper flavor, marinate the chicken for up to 2 hours.