Thinly slice zucchini, tomato and red onion with a mandoline or knife. Add a small amount of olive oil and minced or sliced garlic to the bottom of a casserole dish or ceramic bowl. Layer zucchini, tomatoes and onion in vessel, seasoning each layer with olive oil, fresh herbs, salt and pepper. Cover tightly with a lid or plate and microwave for 4 minutes on high. Add more time if needed. Terrine keeps very well in the fridge for a few days.