In a large mixing bowl, whisk the heavy cream until soft peaks form. Add 1 cup confectioners' sugar, lemon zest, and vanilla extract. Continuing whipping until firm peaks form. Set aside.
In another large mixing bowl, whip together the cream cheese, mixed berry jam, and 1 1/2 cups confectioners' sugar until smooth. Fold into the prepared whipped cream until evenly combined. Divide into three large piping bags. Refrigerate for 15-20 minutes.
Assemble the cake by arranging a layer of RITZ Crackers on a cake plate or serving dish using a springform pan ring as a guide. (The springform pan ring is optional but recommended.) Pipe about 3/4 cup of the mixed berry whipped cream on the crackers. Spread the whipped cream out evenly with a small offset spatula. Repeat the cracker and filling layers until you reach the top of the pan or desired height. The top layer should be the mixed berry cream.
Refrigerate for 4-5 hours or until ready to serve. When ready to serve, top with any extra mixed berry whipped cream and a mound of fresh berries.