Preheat the oven to 300 degrees F.
Grate the zucchini into a bowl using the large grating side of a box grater. Immediately stir in the onion and eggs. Stir in 6 tablespoons of the flour, the baking powder, salt, and pepper. (If the batter gets too thin from the liquid in the zucchini, add the remaining 2 tablespoons of flour.)
Heat a large (10 to 12-inch) saute pan over medium heat and melt 1/2 tablespoon butter and 1/2 tablespoon oil together in the pan. When the butter is hot but not smoking, lower the heat to medium-low and drop heaping soup spoons of batter into the pan. Cook the pancakes about 2 minutes on each side, until browned. Place the pancakes on a sheet pan and keep warm in the oven. Wipe out the pan with a dry paper towel, add more butter and oil to the pan, and continue to fry the pancakes until all the batter is used. The pancakes can stay warm in the oven for up to 30 minutes. Serve hot.