Wrap garlic in foil and bake in 375 degrees for 45 minutes until the garlic is tender and soft. Remove when done and allow to cool.
In a food processor, add the garlic, lemon zest and juice, thyme, cumin, red pepper, salt and olive oil. Pulse until well blended and then rub mixture all over chicken. Allow chicken to rest for at least 30 minutes and up to 2 hours.
In a medium pot, par-cook the couscous. Bring a pot of water to a boil and cook for 5-6 minutes. Drain and set aside.
Next, get a large pot or dutch oven and drizzle with olive oil. On medium heat sear chicken on all sides to brown it. It doesn't have to be cooked all the way through, just seared. When done, reserve to a plate.
Add celery and onions and saute in chicken oil. Season with salt and red pepper. Allow to cook until veggies begin to break down, about 5-6 minutes.
Add wine and deglaze pan using a wooden spoon to scrape the chicken bits from the bottom. Add tomato paste and saffron and mix well. Add zucchini, couscous and chicken stock and stir to combine. Taste for seasoning (more salt?)
Place chicken back in with all its juices. Chicken should not be fully covered under liquid, but slightly sticking out. Cover dutch oven with lid and place in oven at 375 degrees F for 20 minutes. Then remove lid and continue to bake for another 10 minutes.