In mixing bowl, whisk the condensed milk, lemon juice, zest, eggs until well incorporated. Poor mixture into the pan. Whip the meringue by combining remaining 1/4 sugar and egg whites until stiff peaks and spoon on top of the pie, spreading evenly to seal the pie. Bake for about 25 minutes or until top of meringue is golden brown, remove and allow to cool. Cover well with plastic wrap and place in the freezer overnight. To serve, do not defrost. Remove from freezer and run a knife around the edge pie to release the meringue and then release the spring form pan. Run knife in hot water, slice and serve.