FOR THE CRUST: Adjust oven rack to middle position and heat oven to 350 degrees. Process cracker pieces, pretzels, sugar, and salt in food processor until finely ground, about 30 seconds. Add melted butter and pulse until combined, about 8 pulses.

Transfer cracker mixture to 9-inch pie plate. Using bottom of dry measuring cup, press crumbs firmly into bottom and up sides of plate. Place plate on baking sheet and bake until crust is fragrant and set, about 17 minutes. Transfer sheet to wire rack.

FOR THE FILLING: Whisk all ingredients in bowl until fully combined. With pie plate still on sheet, carefully pour filling into crust (crust needn't be cool). Transfer sheet to oven and bake pie until edge of filling is set but center still jiggles slightly when shaken, about 30 minutes.

Place pie on wire rack and let cool completely, about 1 hour. Refrigerate until fully chilled, at least 4 hours, or cover with greased plastic wrap and refrigerate for up to 24 hours.

FOR THE MERINGUE: Combine egg whites, salt, and cream of tartar in bowl of stand mixer fitted with whisk attachment. Whip on medium-high speed until soft peaks form, 2 to 4 minutes.

Combine sugar and water in small saucepan. Bring to rolling boil over medium-high heat and cook until syrup registers 240 degrees, 1 to 3 minutes.

Working quickly, turn mixer to medium speed. With mixer running, slowly and carefully pour hot syrup into egg white mixture (avoid pouring syrup onto whisk, if possible). Add vanilla. Increase speed to medium-high and whip until shiny, stiff peaks form, about 2 minutes.

Spread meringue over pie filling, leaving 1-inch border around pie. Working gently, use spatula or spoon to create swirls and cowlicks over surface of meringue. Sprinkle meringue with lime zest. Slice pie into wedges with wet knife, wiping knife clean between slices. Serve.