Cut the stem ends from the zucchini and grate on the large holes of a box grater.  In a colander, toss the grated zucchini and the salt with your hands and squeeze the zucchini to remove most of its liquid. Remove more liquid by patting it with a paper towel.

In a large bowl, combine the zucchini, chicken, cheese, scallions, red pepper (if using) and hot sauce. Taste the mixture and add more salt and/or hot sauce if needed.

Heat a large cast-iron or nonstick skillet over medium heat.  Working one at a time, warm the tortillas in the skillet until pliable, about ten seconds per side, then transfer to a work surface.  Scoop one-sixth (about 1/4 cup) of the chicken on top of each tortilla and fold in half over the filling.

Spray the skillet with cooking spray.  Add 3 of the quicksadillas and spray the tops with cooking spray. Cook until lightly browned on the bottom and the cheese is melted, about 2 minutes.  Flip and brown the other side, about 2 minutes longer. Repeat with the remaining quicksadillas, adding more cooking spray to the pan as you go.  Serve with a generous dollop of guacamole and/or salsa on the side.