Mix the flour, yeast, sugar, salt and lemon zest well in a bowl. Melt the butter, pour in cold milk and let it cool down to hand warmth. Then use 3 eggs and the flour mixture to form a smooth, shiny, not too firm dough. Cover and let rise for about 45 minutes at room temperature.
Mix the remaining 2 eggs with nuts, raisins, sugar and cinnamon to a creamy mass and set aside. Knead the yeast dough vigorously, roll out into a square with an edge length of 40 cm, spread the hazelnut filling on it, roll up the dough and place in a greased bundt cake pan. Cover and let rise for another 15 minutes. During this time, preheat the oven to 175 degrees (convection).
Bake the Gugelhupf for about 40 minutes until golden.