Preheat the oven to 450°F convection.
Grate the zucchini using the large holes of a box grater or a spiral grater.
Transfer the grated zucchini to cheesecloth and wring it out extremely well, twisting and squeezing repeatedly to remove as much liquid as possible. This step is essential—the zucchini needs to be very dry for the cutlet to get crispy.
In a large bowl, combine the ground chicken or ground turkey breast, wrung-out zucchini, kosher salt, garlic powder, onion powder, dried oregano, black pepper, lemon zest, Parmesan and balsamic vinegar of Modena. Mix until just combined.
Place a large sheet of parchment paper on your work surface and generously sprinkle it with flour.
Add the chicken-zucchini mixture and press it into a very thin, large cutlet, similar in thickness to a pounded chicken breast. Because of the zucchini, the mixture may be wetter and tackier than a standard cutlet, so use additional flour as needed.
Generously dust the exposed surface with flour, adding more anywhere the mixture looks or feels wet or sticky.
Brush the surface with whisked egg, completely cover with panko breadcrumbs, gently press them in and spray generously with avocado oil.
Place another large sheet of parchment over the top and carefully flip the entire cutlet.
Slowly peel away the parchment from the unbreaded side. If the chicken sticks, sprinkle a little more flour directly over the exposed chicken as you peel. Continue slowly until the parchment releases.
Dust the second side with additional flour as needed. You may need more flour than usual because of the zucchini. Brush with egg, completely coat with panko, gently press the breadcrumbs in and spray generously with avocado oil.
Carefully transfer the cutlet to a large sheet pan.
Bake at 450°F convection for 15 minutes, until golden, crispy and cooked through.
Remove from the oven and immediately grate fresh Parmesan generously over the hot cutlet. Finish with flaky sea salt. Do not broil.
Let rest for a couple of minutes before slicing.