Heat the oil in a large frypan over a medium-high heat. Add onion, garlic, carrot, celery and bacon; cook, stirring, for about 5 minutes or until softened. Add pork and veal; cook, stirring, until browned. Add wine, cook, stirring, for about 20 minutes. Add tomato paste and chopped tomatoes; simmer, uncovered, for 2 hours or until very thick. Season well with salt and freshly ground black pepper.

Meanwhile, to make cheese sauce, melt butter in a medium saucepan over a medium heat. Add flour; cook, stirring, for 1 minute or until mixture thickens and bubbles. Gradually add milk, stirring constantly. Cook, stirring, until the mixture boils and thickens. Stir in the nutmeg and the parmesan.

Preheat oven to 200°C (180°C fan-forced). Spoon mince mixture into a large, shallow, ovenproof dish. Slice zucchini lengthways. Arrange zucchini slices, overlapping slightly, onto mince mixture, then spread the cheese sauce over top. Sprinkle with the mozzarella.