In a large bowl, beat cream cheese, confectioners' sugar, vanilla and lemon zest until fluffy. Fold in whipped cream. Divide among 12 dessert dishes. Cover and refrigerate at least 2 hours., Meanwhile, preheat oven to 375°. Combine cracker crumbs and sugar in a small bowl; add butter and mix well. Press to a 1/4-in. thickness on an ungreased baking sheet. Bake until lightly browned, 10-12 minutes. Cool completely. , Just before serving, crumble graham cracker mixture; sprinkle over mousse. Top with strawberries if desired.