Par-bake pie crust according to package instructions. Let cool. Leave oven to preheat at 375℉.
In the ready-made pie crust, smear about 2 teaspoons of mustard all over the bottom.
In a large skillet on medium to medium high add butter, zucchini, onion, dried parsley or basil, salt and pepper, garlic, and oregano. Cook until translucent.
Switch off the heat to the skillet and add in eggs and cheese. Stir to combine and immediately pour into prepared pie crust.
Smear about 2 more teaspoons of the same mustard as before all over top.
Bake for 18 to 20 minutes or until set and a knife pulls away clean. If clumpy, give an extra 5 minutes.
Let cool a bit before enjoying!