1. Preheat the oven to 200 °C (th. 6/7). Place the sweet potato wedges on a baking sheet. Season and bake for 25 minutes until crispy and golden.
2. Meanwhile, put the onions, zucchini, chickpeas, roughly chopped garlic, parsley, coriander, cumin, baking powder, and harissa in a food processor. Season and blend until all the ingredients are well mixed. Form 12 balls and roll them in sesame seeds.
3. Heat the oil in a large non-stick skillet over medium/high heat. Cook the falafels for 1 to 2 minutes on each side, then transfer them to an ovenproof dish and bake for 10 minutes.
4. Spread each pita bread on a plate and add the tomato wedges, arugula leaves, 3 falafels, and some sweet potato wedges. Mix the finely chopped garlic with the tzatziki and spread a little on each bread. Roll the pita bread tightly and serve with the remaining arugula leaves, sweet potato fries, and tzatziki.