For the crust, combine the zwieback crumbs, 1/3 cup sugar, nutmeg, and melted butter. Press onto bottom and part way up sides of a 9-inch springform pan. Chill crust while preparing filling.
Preheat oven to 450 degrees F (230 degrees C).
For the filling, beat cream cheese in large mixer bowl until fluffy. Stir in Colby cheese, 3/4 cup sugar, flour, milk, vanilla, and salt. Beat on medium speed of mixer until well-blended, about 3 minutes. Beat in eggs, one at a time, beating well after each addition. Pour into chilled crust. Bake for 10 minutes.
Reduce oven temperature to 250 degrees F (120 degrees C). Bake until the center of the cheesecake is set, about 40 minutes.
Remove from oven and let stand 10 minutes. Spread yogurt over top. Return to oven and bake 10 minutes. Cool completely on wire rack. Chill several hours or overnight. To serve, place the cake on a serving plate and carefully remove the sides of the pan.