1.Place zucchini, cabbage, carrot and celery in a large bowl; toss gently to combine.
2.To make lemon dressing, whisk oil, juice and garlic in a small jug; stir in basil and mint. Season.
3.Add lemon dressing to zucchini mixture; toss gently to coat. Season.
4.Serve slaw sprinkled with walnuts.
Use a vegetable peeler to shave zucchini into long, thin ribbons, or coarsely grate. Add walnuts just before serving, to give salad a nutty crunch. To transport: Carry salad and dressing separately in airtight containers. Cover and keep chilled. Place walnuts in a small, resealable food storage bag, then transport separately. Toss together just before serving.