Place grated zucchini in a colander over the sink. Add 1 teaspoon salt and gently toss to combine; let sit for 10 minutes. Using a clean dish towel or cheese cloth, drain zucchini completely.
In a large bowl, combine zucchini, flour, Parmesan, garlic and egg; season with salt and pepper, to taste.
Heat olive oil in a large cast iron skillet over medium high heat. Working in batches, scoop 3-4 tablespoons of batter for each fritter, flattening with a spatula, and cook until the underside is nicely golden brown, about 2 minutes. Flip and cook on the other side, about 1-2 minutes longer.
Serve immediately.
Notes
Squeeze dry the zucchini. This is a key step to avoid soggy fritters! Grate the zucchini and add 1 teaspoon salt. The salt not only seasons the zucchini beforehand but also draws out the excess moisture. Wrap the grated zucchini in a clean dish towel or cheese cloth and squeeze out as much liquid as possible.
Cook in batches. Work in batches to properly cook the fritters for maximum crispness. An overcrowded pan will unfortunately steam the fritters instead.
Mix it up. Use a different kind of cheese (ex. feta or cotija), add fresh herbs (thyme, rosemary, oregano or dill) or fresh lemon zest to brighten up some of the savory flavors.
Keep warm. The fritters can be kept warm in a low oven at 250°F.
Reheat in the oven. Leftover fritters can be soggy when reheated. For best results with leftovers, reheat in the oven at 350°F until warmed through, about 5-10 minutes.
Freeze leftovers. Flash-freeze the fritters first, then transfer to an airtight, resealable freezer bag, freezing up to 3 months.