Remove the thyme sprig from the broth mixture. Over medium heat, add the broth to the quinoa, about 1 cup (250 ml) at a time, stirring frequently, until the liquid is completely absorbed before adding more broth. Season with salt and pepper. Cook for 20 minutes or until the quinoa is cooked. Add more broth, as needed. Stir in the peas, chives and lemon zest.