In a large bowl, toss pretzels with sugar and melted butter. Press into an ungreased 13x9-in. dish. Refrigerate 30 minutes., In a large bowl, beat cream cheese, ricotta, confectioners' sugar, vanilla and grated lemon zest until smooth. In another bowl, beat heavy cream until stiff peaks form; fold into cream cheese mixture., Spread over pretzel layer. Refrigerate, covered, at least 4 hours. Just before serving, toss berries with apricot preserves if desired; sprinkle over top of dessert. If desired, top each serving with additional whipped cream and miniature pretzels.