Puree the strawberries in a blender or food processor until smooth, then set aside.
In a chilled mixing bowl, beat the heavy cream with powdered sweetener until stiff peaks form, about 3-4 minutes.
In a separate bowl, beat the softened cream cheese with vanilla extract and lemon zest until smooth and fluffy.
Gently fold the strawberry puree into the cream cheese mixture until well combined.
Carefully fold the whipped cream into the strawberry mixture in two additions, being careful not to deflate the mousse.
Spoon into individual serving glasses and refrigerate for at least 2 hours before serving.