In the bowl of an electric mixer, combine the sugar cookie mix and cream cheese. Add the flour in 3 parts. Add eggs and lemon extract, and mix until just incorporated. Fold in the in lemon zest.
On lightly floured surface, roll out dough to a 12 by 14-inch rectangle. Using a fluted pastry cutter, cut dough into 2-inch squares.
Place cutouts 1-inch apart on ungreased cookie sheet. Freeze 10 minutes. Bake for 10 to 12 minutes, until bottoms are golden brown and tops are set. Cool completely on cooling rack. Dust with powdered sugar.