Whisk together the flour, salt and pepper in a large bowl. In a separate small bowl, whisk together the egg yolks and vegetable oil. Drizzle the egg and oil mixture over the flour and mix together with a fork to create a shaggy dough. Slowly pour in the beer while constantly whisking, until a smooth batter forms. Cover with plastic wrap and refrigerate for at least 1 hour (up to 4 hours) before frying.
Heat the oil in a large Dutch oven until it reaches 375 degrees F. Working with one batch of zucchini fries at a time, drop them into the batter, making sure each one is coated. Using tongs, gently add them to the oil and fry until golden brown, about 4 to 5 minutes. Remove from the oil with a slotted spoon and drain on a paper towel-lined pan. Allow the oil to come back up to temperature, and then repeat until all of the zucchini has been fried. Serve with ranch dressing or a spicy mayonnaise.