Slice the zucchini and mushrooms into 7mm thick slices. Peel sweet pepper from seeds and partitions, cut into slices. Peel the onion and cut into rings 7-8 mm thick. Arrange vegetables on a baking sheet, season with salt and pepper and drizzle with olive oil.
Heat up a grill pan and sauté the vegetables for 2-3 minutes. on each side, they should remain crispy. Transfer cooked vegetables to a board, let sit 5 minutes, then cut into large pieces.
Brush each tortilla with pesto. Put some mozzarella on half of the tortilla, then a layer of vegetables, mozzarella again and cover with the second half of the tortilla.
Place the tortillas on a preheated grill pan lightly brushed with olive oil and fry for 3 minutes. on each side until cheese is melted. Cut the tortillas into 3-4 pieces and serve immediately.