Grate zucchini either on a box grater (using the largest holes) or with the grating blade of a food processor.
Place grated zucchini in a clean kitchen towel, squeeze out all excess moisture, and discard liquid.
Place drained zucchini in a large mixing bowl.
Add scallions, garlic, herbs, salt, black pepper, red pepper flakes, and mix to combine.
Add eggs, panko bread crumbs, and parmesan cheese.
Mix until well combined.
Preheat a 10” nonstick sauté pan over medium heat with 2T of vegetable oil.
Working in batches, portion 1/3 C of zucchini mixture into a patty and add to heated sauté pan.
Cook until first side is nicely browned, approximately 7-8 minutes.
Flip. Continue cooking until second is browned. It should take an additional 5-6 minutes.
Remove from pan and place on a baking sheet, lined with paper towel for draining.
Add 2 more tablespoons of vegetable oil to sauté pan and cook the remaining zucchini cakes in the same manner.
(You can place the finished zucchini cakes into a 200° F oven while you continue cooking additional batches).
To serve, to with a dollop of sour cream and additional chopped scallions, if desired.