Cut the chicken breast and beef sirloin into uniform 1-inch cubes for even cooking.
In a small bowl, whisk together the olive oil, minced garlic, dried oregano, dried parsley, sea salt, and black pepper to create the marinade.
Place the meat cubes in a glass bowl and toss with half of the prepared marinade; allow it to marinate for at least 15 minutes.
While the meat marinates, chop the bell pepper, red onion, and zucchini into 1-inch chunks.
Thread the marinated meat and vegetables onto skewers, alternating between the chicken, beef, and various vegetables.
Preheat a grill or grill pan to medium-high heat and lightly grease the surface to prevent sticking.
Grill the skewers for 10-12 minutes, turning occasionally, until the chicken and beef are cooked through and the vegetables are tender with a light char.
Brush the skewers with the remaining marinade during the final 2 minutes of cooking for an extra burst of herbal flavor.