Heat oil in a large frypan. Fry zucchini until brown on both sides. Set aside.
Place water in large frypan over medium heat. Sauté onion and garlic until soft.
Topping: Mix together eggs, yoghurt and extra basil in a small bowl.
To assemble, cover the base of a shallow casserole dish with half the lentil mixture. Cover with half the zucchini. Repeat, finishing with zucchini. Pour over topping. Sprinkle with cheese.
Bake in a moderate oven for 30-40 minutes, or until browned.
Serve with steamed vegetables and herb bread, if desired.