Heat the oil in a large deep skillet or a wide pot over medium-high heat.
Season the chicken thighs with salt and pepper on both sides, place them in the pan, and cook them for 2-3 minutes on each side, until they brown thoroughly. Remove chicken to a clean bowl, reserving any juices (at this point the chicken should not be fully cooked).
In the same skillet, add the onions and saute, stirring occasionally, until slightly browned, about 10 minutes. Remove onions to the bowl containing the chicken.
If necessary, add a bit more olive oil to the skillet and let it get hot. Add the sliced zucchini and saute, stirring occasionally, until slightly browned.
While the zucchini is cooking, measure the spices (cayenne pepper, chili powder, cumin, cinnamon, ginger and coriander) into a small bowl and combine.
Add the chicken and onions, along with the collected juices, back to the pan. Add the garbanzo beans, tomatoes with their juices, spices, and chicken stock. Stir gently to combine.
Turn heat to high until the stew gently boils. Immediately reduce heat to medium and simmer for 10 to 15 minutes, until the chicken is cooked through.
While the dish simmers, prepare the couscous according to package directions.
Just before serving the chicken, add the juice of one lemon (about 1 1/2 Tbsp).
Season to taste with more salt and pepper.
Serve over whole wheat couscous garnish with fresh chopped cilantro.