Put sausage in a pan with oil and half a cup of water. Cook, covered, until water is mostly gone. Remove and cook, turning frequently, for 6 to 8 more minutes. Remove from pan and set aside to cool.
In same pan, add onion, salt, and pepper. Cook for 1 to 2 minutes, scraping up the fond.
Add zucchini and cabbage and cook for 2 to 3 minutes
Add tomatoes and cook for 1 to 2 minutes
Slice sausage into bite sized pieces
Add sausage and cook, covered, until sausage is fully cooked and tomatoes are soft.
Garnish with harissa and green onions.