In a mixing bowl, combine the flour and salt. Make a well in the center. In a separate bowl, beat the eggs, sugar, melted butter, and citrus zest (if using) until well combined. Pour the egg mixture into the well of the flour, add the wine/brandy, and start mixing with a fork or your hands, then kneading until a smooth dough forms. Add more flour as needed if the dough is too sticky. Knead the dough for a few minutes until it's elastic and smooth.
Wrap the dough in plastic wrap and let it rest at room temperature for about 30 minutes. This helps relax the gluten and makes it easier to roll out.
While the dough rests, line a large dish or small tray with paper towels and set aside (you will use this to drain the fried crostoli). Begin to heat enough oil to fry the crostoli in a Dutch oven or a deep fryer.
After the dough has rested, divide it into four pieces on a lightly floured surface. Roll out one portion as thin as possible. Lightly flour each side as you roll and flip the dough ocassionally to avoid sticking.
Alternatively, if using a pasta machine, flatten a portion of rested dough by hand, then feed it through the widest setting, 0. Fold it into thirds and repeat 2-3 times until smooth. Without folding, run the dough through progressively narrower settings (1, 2, 3, 4) until reaching setting 5.
Cut the dough sheets into strips. I use a ravioli/pastry wheel to cut the dough into about 1-inch-wide strips, but you can also use a knife.
After the vegetable oil has reached about 350°F (175°C), carefully slide a few crostoli at a time into the hot oil. Fry them until lightly golden and crispy. They can get dark rather quickly, so keep watch. Use a slotted spoon to remove the crostoli from the oil and place them on a plate lined with paper towels to drain excess oil.
While warm, dust them generously with powdered sugar. You can do this by placing powdered sugar in a fine-mesh sieve and tapping it over the crostoli or by using a powdered sugar shaker.
Crostoli are best enjoyed on the day they're made, but I find they will maintain their crispiness for a few days if sealed in an air-tight container or in a cardboard box lined with paper towels.