1.Coarsely grate zucchini. Drain and finely chop tomatoes.
2.Oil deep 20cm (8-inch) square cake pan, line base and sides with baking paper.
3.Bring the water and stock to the boil in large saucepan, gradually stir in polenta. Reduce heat, simmer, stirring, about 10 minutes or until polenta thickens. Stir in zucchini, tomatoes, olives and cheese. Spread polenta mixture into pan, cover, refrigerate about 1 hour or until polenta is firm.
4.Turn polenta onto board, cut in half. Cut each half into six slices.
5.Heat oil in large frying pan, cook polenta until browned both sides.