I use more zucchini than the original recipe called for. I have Longaberger pie plates and they are large and will hold this easily. If you have a small-ish pie plate you may want to cut the zucchini amount back to 1 1/2 cups or even 1 cup.
I don't turn my oven back to 300° but to just above 325° - my oven is too cool at that low a temp and it takes forever to get the pie set. Adjust accordingly for your oven.
Don't have evaporated milk? Use Cream. Or 1/2 and 1/2. Or whole milk.