Warm milk and buttermilk in the microwave until slightly warm but not hot. Pour in a large bowl. Sprinkle yeast on top. Let it sit for 5 minutes. Add sugar, salt, vanilla, zest and eggs. Attach dough hook and turn on the machine. Add the AP flour, and the bread flour, one cup at a time. After the flour is in, add the softened butter a tablespoon at a time. Let the dough kneed for a few minutes. Place the dough in an oiled bowl, cover with plastic wrap and place in the refrigerator overnight. The next day, divide dough into 4 pieces.
Roll out one piece of dough into a rectangle. Trim the edges to make it more exact.