In a large mixing bowl, combine the olive oil, minced garlic, lemon juice, za'atar, and kosher salt. Add the chicken thighs and toss to coat them evenly in the marinade. Cover and let marinate in the refrigerator for at least 30 minutes or up to 2 hours for maximum flavor.
In another bowl, whisk together the tahini, olive oil, fresh lemon juice, minced garlic, and kosher salt. If the sauce is too thick, add cold water one tablespoon at a time until you reach your desired consistency. Set aside.
Preheat your oven to 425°F (220°C). On a sheet pan, toss the chopped zucchini, red bell pepper, red onion, and broccoli with a drizzle of olive oil and a pinch of salt. Spread them out in an even layer and roast for about 20-25 minutes, or until the veggies are tender and slightly caramelized.
While the vegetables are roasting, heat a grill pan over medium-high heat. Remove the chicken from the marinade, letting any excess drip off, and place them in the hot pan. Cook for about 6-7 minutes per side, or until the internal temperature reaches 165°F (75°C). Once cooked, remove from the pan and let rest for a few minutes before slicing.
To serve, start with a base of cooked white rice or cauliflower rice in each bowl. Top with sliced chicken thighs, roasted vegetables, and drizzle over the creamy tahini sauce. Finish with a sprinkle of fresh parsley and mint for a burst of color and freshness.
