Heat olive oil in a large frypan over medium-high heat. Add chicken thighs, skin-side down, and sear until golden brown on both sides; set aside. Reduce heat to medium, add sausage, and cook sausage until no longer pink; set aside.
Stir garlic and onions into frypan; cook until onions have softened and turned translucent. Stir in the carrots, celery, parsnip, capsicums, diced tomatoes, chickpeas, and 2 cups chicken stock. Season with thyme, turmeric, cayenne, harissa, and bay leaf. Cut sausage into 2cm pieces, and add to frypan along with chicken. Cover, and simmer for 30 minutes until chicken is no longer pink. When the chicken is done, stir in the zucchini, and cook until tender, about 5 minutes.
While the chicken is cooking, mix 2 tablespoons of extra virgin olive oil (EVOO) into couscous in a heatproof bowl. Bring 2 cups of chicken stock to a boil and stir into the couscous, cover, and keep hot.
Serve chicken stew over the couscous with a dollop of yoghurt.