For the churros with vanilla ice cream, first for the dough, bring water, butter and salt to a boil in a medium saucepan.
Once the butter has melted, reduce the heat and add the flour in one piece. Stir constantly until a white coating forms on the bottom of the pot and the dough separates well.
Now remove from heat and let cool slightly. Add the first egg and stir it in. The mixture will look a little lumpy now. Just keep stirring until everything is neatly combined. Then gradually add the rest of the eggs and the zest of an orange and lemon and keep mixing until the batter is viscous and glossy.
Fill the mixture into a piping bag with a star-shaped nozzle and pipe 10 cm long bars onto a baking tray lined with baking paper. Leave to set in the freezer for about 30 minutes.
In the meantime, mix granulated sugar and cinnamon in a bowl. Fill a deep frying pan about 2/3 full with vegetable oil and slowly heat to about 170°C. It is best to test with a wooden stick and dip it into the oil. If small bubbles rise, the oil is hot enough.
Remove the churros from the freezer and fry them in batches in the hot oil until golden brown. Do not put too many in the oil at once, or it will cool too much. Drain on paper towels and roll in the cinnamon-sugar mixture.
Serve the churros still warm with vanilla ice cream.