Whisk together flour, granulated sugar, salt, mace, and nutmeg in a large bowl. Stir in milk and melted butter. Add dissolved yeast and the eggs. Turn out onto a lightly floured surface, and knead until smooth.
Drain raisins and currants. Add raisins, currants, almonds, citron, orange peel, apricots, and lemon zest to dough, and continue kneading until incorporated, about 10 minutes. If dough is sticky, knead in more flour.
Transfer dough to a lightly oiled bowl. Cover with plastic, and let rise in a warm place until doubled in volume, 1 to 2 hours.
Punch down dough, divide into 6 even pieces, and roll each piece into a 15-inch-long log. Braid 3 logs together, and place on a parchment-lined baking sheet. Repeat with remaining 3 logs.
Cover with plastic, and let rise until doubled in volume, about 2 hours more.
Preheat oven to 350 degrees. Bake stollen until golden brown, 35 to 40 minutes. Let cool completely on a wire rack. Beat together confectioners' sugar and milk. Drizzle stollen with icing just before serving.