Add marinade ingredients to a large zip-top bag and add chicken. Seal bag and using your hands, press down on the chicken to distribute marinade evenly. Refrigerate for 45 minutes to 2 hours.
Heat grill or grill pan to medium-high heat.
Thread the chicken onto metal or presoaked wooden skewers (about 30 minutes in water).
Brush the grates with olive oil then place the skewers over top. Grill the chicken for 3-4 minutes per side, gently flipping and cook for another 3-4 minutes, until chicken is cooked through and has light char marks.
While the chicken is grilling, toss the zucchini, bell peppers and tomatoes onto the grill and cook for about 3-4 minutes on each side, or until the desired doneness.
Divide the cauliflower rice among bowls. Top with grilled vegetables, olives, and chicken skewers.
Sprinkle with feta cheese and serve with Tzatziki sauce.
Tzatziki sauce
Combine all the ingredients by hand or a blender (if you want it smooth). Cover and refrigerate until ready to use.