Prepare eggplant and potato by cubing them and letting them stand (separately) in salt water for 15 minutes. 1 tablespoon salt to 2 qts of water is enough. This extracts the excess moisture from them and makes them easier to cook. Drain, rinse, and pat dry.
The easiest way to peel tomatoes is to blanch them in boiling water for a few seconds until the skin starts to peel away. The skin will fall off without much effort.
Put some olive oil in a dutch oven and sautee first 5 ingredients separately. First sautee the onions until wilted, then remove them from the pan. Then sautee the zucchini until wilted, then remove from the pan and put together with the onions. Then sautee the eggplant together with the peppers. Remove from pan. Then the potatoes. Potatoes only need to be half cooked. You can add olive oil as needed/desired for sauteeing. After the potatoes are half cooked, add the other sauteed ingredients back to the dutch oven, add the garlic, bouillion, tomatoes, tomato paste, and parsley. Add hot water so the liquid is about 1 inch below the top of the mixture. Simmer for 30-40 mins until potatoes are done. You may need to add more water from time to time.