Line a 9×13-inch springform pan with plastic wrap
Crush graham crackers into coarse crumbs (8 cups total)
In a mixing bowl, combine graham crumbs, sweetened condensed milk, lemon juice, and lemon zest
Press ¾ of the mixture evenly into the pan
Spread remaining mixture on top
Chill for 2 hours
In a separate bowl, whip heavy cream until stiff peaks form
Lay plastic wrap over dessert, gently press whipped cream layer into place
Chill 4-5 hours until firm
Run a knife around edges before slicing and serving