For the cinnamon sugar: Whisk the sugar and cinnamon in a medium mixing bowl until combined. Set aside.
For the crullers: Bring the milk, water, butter, sugar and salt just to a boil in a large saucepan over medium-high heat and stir together. Add the flour and quickly stir it in with a silicone spatula or wooden spoon. Continue to cook, stirring constantly, until the mixture starts to pull away from the sides of the pan, about 3 minutes. Transfer to the bowl of a stand mixer fitted with the paddle attachment.
Starting on speed one, beat the mixture for a few minutes until cooled slightly. Add the eggs and egg white, one at a time, allowing the egg to fully incorporate before adding the next. Add the lemon zest and mix to incorporate. Scrape the batter from the paddle attachment, then using a silicone or rubber spatula, scrape the sides of the bowl to make a smooth batter. Let the batter sit while preparing the oil.
Heat the oil in a large (6-quart) Dutch oven or tabletop fryer to 360 degrees F. Cut a sheet of parchment paper into ten to twelve 3-by-3-inch squares. Lay the papers on a baking sheet and spray lightly with nonstick baking spray. Fit a large star tip into a piping bag and fill with the cruller batter. Pipe a uniform circle onto each parchment square, overlapping the batter as you finish the circle.
Once the oil has reached temperature, carefully place 3 of the crullers into the oil, batter-side down. Remove each of the parchment squares with tongs. Fry on the first side until the batter starts to erupt on the top, about 5 minutes. Flip over with tongs and fry on the second side until golden brown, another 5 minutes. Remove from the oil and drain on a paper towel-lined plate. Toss the hot crullers immediately in the cinnamon sugar. Repeat with the remaining crullers.