Preheat oven to 425 F.
Preheat a skillet over medium-high heat with 2 tablespoons of EVOO. Add zucchini and saute until golden brown, about 5 minutes. Add the scallions, shredded chicken and tomatillo salsa, and cook until heated through. Season with salt and pepper.
While the filling is cooking, place the tortillas on 2 cookie sheets in an even layer, making sure not to overlap. Lightly brush them with some EVOO and bake until crispy, about 6 minutes. Remove tortillas from the oven and top each one with an even amount of filling followed by a handful of the cheeses.
Return the tostados to the oven to melt the cheese. Garnish with chopped cilantro and serve. Yum-O!