Combine 3 cups sliced strawberries, sugar and juice in a medium saucepan.
Mash berries in pan with a potato masher; stir in cornstarch and bring mixture to a boil over medium-high heat. Reduce heat to medium-low and cook, stirring often, until very thick, about 1 minute.
Remove from heat; let cool slightly and then stir in remaining sliced strawberries. Scrape into pie crust.
Let cool slightly; cover loosely with plastic lid from pie crust. Refrigerate until set, at least 4 hours (you can then freeze the pie for a little while if desired, to make it easier to slice).
To serve, in a medium bowl, stir together vanilla yogurt and lemon zest until blended. Spread on top of pie, leaving a border around edges so strawberry filling shows. Slice reserved strawberries and use them to garnish pie. Slice pie into 10 pieces and serve. Yields 1 piece per serving.