Wash the potatoes thoroughly, scrub if necessary, dry and cut into eighths. Wash the peppers and zucchini, brush the mushrooms, peel the garlic and onion. Clean the peppers, cut them into six and cut them into strips, cut the zucchini in half lengthwise, then cut them into quarters and cut them into pieces. Cut the onion into quarters and cut it into thin strips, quarter or sixth of the mushrooms depending on their size, finely chop the garlic.
Mix the tomato paste first with water, then with oil, spices, garlic and herbs. Mix the potatoes with half of the marinade and put in the oven at 170 to 180 degrees for 20 minutes in a casserole dish, mix the rest of the marinade with the vegetables. Remove the baking dish after about 20 minutes, add the marinated vegetables and mix with the potatoes. Put them back in the oven together for 15 minutes.
If you like, you can then grate it with freshly grated parmesan for a few minutes