Preheat oven to 446 °F / 230°C.
Rinse and prepare all the veggies. Cut off the ends of the zucchinis and peppers.
Slice off the top of each vegetable about 1-2 cm.
With a pointy tablespoon scoop of the tomato insides and set aside.
Remove any seeds and white membranes from the peppers leaving their insides clean.
Using a melon baller or a sharp knife, remove most of the inside flesh of the zucchinis and eggplants and discard it. Leave a 1-2cm thick wall lining on the veggies.
Place all veggies in a large pan leaving enough space around them to place the potatoes.
Using a spoon fill each vegetable completely and place its top back on.
Add the potatoes all around the veggies to hold them in place.
Add just a drop of water in order to cover the bottom of the pan.
Pour the olive oil and season the veggies and potatoes with salt and pepper.
Cook for about 1 hour. After the first 20-25 minutes of baking, cover the pan with aluminum foil to prevent veggies from burning on top.