Place zucchini into a food processor and pulse until finely chopped. Transfer to a large bowl. Repeat with carrot, capsicum, and eggplant, processing each vegetable separately to prevent them becoming soft and mushy.
Prepare pasta according to packet instructions.
Meanwhile, heat oil in a deep saucepan over a medium heat. Add garlic, along with vegetables and fry, stirring occasionally, 10mins. Stir in passata and 1 cup water, bring to the boil, reduce heat, simmer 20mins, or until vegetables are very soft and sauce is thick and rich. Season with salt and pepper.
Serve hot over just drained pasta.