The origin of stuffed vegetables is unknown, although the Turks and Greeks claim possession. Originally, they were served in palace kitchens to the wealthy and ruling class. Nowadays, there are various recipes for stuffed zucchini, but this one is an Iranian version of it.
Preheat oven to 175 degrees C (350 degrees F).
Slice the zucchinis lengthwise and scoop out the seeds and center to form a "boat" . Reserve the center flesh. Season the zucchini slices with salt and pepper to taste.
Meanwhile, heat vegetable oil in a large skillet over medium heat. Chop the onion and saute together with the reserved zucchini flesh.
Chop the green pepper and add to the skillet. Saute for 2 minutes.
Chop tomato and mushrooms and add to the mixture with the shredded chicken. Add salt and pepper to taste. Saute for 5 minutes over medium heat and then remove from the heat.
Stuff the mixture into the hollowed-out zucchini. Bake in the preheated oven for 30 minutes.
Remove from oven and sprinkle each with about 1 tablespoon of Parmesan cheese. turn on the broiler, and broil the zucchini until cheese is browned and bubbling, about 5 minutes.