Place a rack in center of oven; preheat to 350°. In a large bowl, using a handheld mixer on medium-high speed, beat milk, egg yolks, and sour cream until smooth. Add lime zest and juice and beat until just combined.
Pour lime mixture into graham cracker crust. Bake pie until crust is darkened and fragrant and filling slightly puffs and center is still a little jiggly, about 15 minutes.
Let cool 30 minutes, then refrigerate until cold, at least 2 hours or up to overnight.
In a large bowl, using handheld mixer on medium-high speed, beat cream and sugar until stiff peaks form.
Top pie with whipped cream, lime zest, and lime slices.
