Preheat oven to 120C. Combine cinnamon, sugar and 10gm fine sea salt in a bowl. Rub over pork belly, drizzle with olive oil, then place in a roasting tray and roast until very tender (3-3½ hours). Cover with baking paper, weighed with heavy food cans, cool and set aside. Then cut into 6 pieces.
Meanwhile, for melomakarona crumble, increase oven to 160C. Beat butter, oil and icing sugar in an electric mixer until pale and fluffy (8-10 minutes). Add walnuts, juice, brandy and spices and beat for 2 minutes, then add flour and baking powder and beat until smooth. Spread on a baking paper-lined oven tray and bake, stirring occasionally, until golden (20-25 minutes). Set aside to cool.
Meanwhile, for moussaka vinaigrette, preheat a chargrill pan over high heat and cook eggplant, turning occasionally, until soft (25-30 minutes). Cool, then peel (discard skin) and process in a blender until smooth. Heat a pan over low-medium heat, add oil, shallot and garlic and sweat until soft (3-5 minutes). Add capsicum and zucchini, and stir until tender (3-5 minutes). Remove from heat, add vinegar and eggplant and season to taste.
Combine quince paste and 100ml water in a small saucepan and stir over medium-high heat until smooth. Set aside.
Preheat a grill to high and grill pork, skin-side up, until fat renders (2-3 minutes) then transfer, skin-side down, to a baking paper-lined frying pan. Cook over low heat until skin is crisp (8-10 minutes). Divide quince mixture and pork among serving plates, scatter with crumble, spoon vinaigrette to the side and serve immediately with yoghurt.