01 - In a large bowl, whisk together olive oil, lemon juice, Greek yogurt, garlic, red wine vinegar, oregano, thyme, salt, black pepper, and lemon zest until well combined.
02 - Add the chicken cubes to the marinade and toss to coat thoroughly. Cover and refrigerate for at least 1 hour, or up to 8 hours for the best flavor development.
03 - If using wooden skewers, submerge them in water for 30 minutes to prevent burning on the grill.
04 - Thread the marinated chicken pieces, red onion chunks, bell pepper pieces, and zucchini rounds onto the skewers, alternating ingredients evenly.
05 - Preheat an outdoor grill or grill pan to medium-high heat. Lightly grease the grates with oil to prevent sticking.
06 - Place the skewers on the grill and cook for 6 to 8 minutes per side, turning once, until the chicken is cooked through and lightly charred on the edges.
07 - Transfer the kabobs to a platter and serve immediately with lemon wedges, a sprinkle of fresh parsley, and tzatziki sauce on the side.