In a large skillet over medium high heat, brown sausage. Add onion, celery, and zucchini and kale to sausage, stir for about a minute and then transfer to crock cooker. Add the broth, salt, pepper and herbs.
Cook on LOW for 5 hours or HIGH for 3 hours. Add the spinach to crock cooker, stir to combine. Cook on high for another 30 to 60 minutes and then serve.