In a large mixing bowl, beat the softened cream cheese with a hand mixer until smooth and fluffy, about 2 minutes.
Add the instant lemon pudding mix, lemon juice, lemon zest, and vanilla extract. Mix until fully combined.
Slowly pour in the cold milk while mixing until smooth and creamy with minimal lumps remaining.
Fold in the Cool Whip using a rubber spatula until light and fluffy.
Spread a thin layer of the lemon filling onto the bottom of a 9x13 baking dish.
Add a layer of graham crackers, breaking them as needed to fit.
Spread about one-third of the lemon filling over the graham crackers.
Repeat the layers of graham crackers and lemon filling until all the filling is used, finishing with lemon filling on top.
Cover and refrigerate overnight or chill for at least 6 hours until set.
Before serving, top with extra lemon zest, berries, graham cracker crumbs, or whipped cream.