Marinate the chicken: In a bowl, whisk olive oil, lemon juice and zest, garlic, oregano, cumin, smoked paprika, salt, and pepper. Add chicken and coat well.
Marinate for at least 20–30 minutes, or up to 8 hours in the fridge.
Make the tzatziki: Stir together Greek yogurt, grated cucumber, lemon juice, olive oil, garlic, dill, salt, and pepper. Adjust seasoning to taste. Chill until serving so the flavors meld.
Prep the veggies: Slice tomatoes, dice cucumber, thinly slice red onion, and halve olives.
Crumble the feta and chop the herbs.
Cook the cauliflower rice: Heat 1 tablespoon olive oil in a large skillet over medium heat. Add cauliflower rice, season with salt and pepper, and sauté 4–6 minutes until tender with a little bite. Set aside. (If using greens, simply dress lightly with lemon and olive oil.)
Cook the chicken: Heat a grill pan or skillet over medium-high heat.
Cook chicken 4–6 minutes per side (thighs may need a touch more) until browned and cooked through. Let rest 5 minutes, then slice.
Assemble the bowls: Divide cauliflower rice or greens between bowls. Top with sliced chicken, tomatoes, cucumber, red onion, olives, and feta.
Spoon over tzatziki and finish with chopped parsley or dill.
Taste and adjust: Add a squeeze of lemon, a drizzle of olive oil, or a sprinkle of salt if needed.