In a large bowl, combine 2 cups of the flour and the yeast. In a medium saucepan, heat and stir milk, water, the 1/2 cup butter, the 3 tablespoons sugar, and salt just until warm (120 degrees F to 130 degrees F) and butter almost melts. Add milk mixture to flour mixture along with the eggs, lemon peel, and orange peel. Beat with an electric mixer on low to medium speed for 30 seconds, scraping bowl constantly. Beat on high speed for 3 minutes. Using a spoon, stir in 1 cup of the sliced almonds and as much of the remaining flour as you can.
Turn dough out onto a lightly floured surface. Knead in enough of the remaining flour to make a moderately soft dough that is smooth and elastic (3 to 5 minutes total). Shape dough into a ball. Place dough in a lightly greased bowl, turning once to grease surface of the dough. Cover; let rise in a warm place until nearly double in size (about 1 hour).
Punch down dough. Turn out onto a lightly floured surface. Cover; let rest for 10 minutes. Meanwhile, lightly grease a 10-inch fluted tube pan; set aside.
For filling, in a small bowl combine the 6 tablespoons softened butter, the 2/3 cup sugar, and the cinnamon.
Roll dough into a 20x12-inch rectangle. Spread filling evenly over dough to within 1/2 inch of edges. Sprinkle filling with remaining almonds. Roll up rectangle, starting from a long side. Seal seam. Carefully place dough, seam side down, in prepared pan, bringing ends together to form ring. Cover and let rise in a warm place until nearly double in size (about 45 minutes).
Preheat oven to 350 degrees F. Bake for 50 to 55 minutes or until golden, covering with foil the last 15 minutes of baking to prevent overbrowning. Carefully invert tube pan onto a wire rack. Remove bread from pan and cool thoroughly. Drizzle with Powdered Sugar Icing.
Powdered Sugar Icing
In mixing bowl combine powdered sugar, vanilla, and milk or orange juice. Stir in additional milk or juice, 1 teaspoon at a time, until it reaches drizzling consistency. Makes 1/2 cup.