Would it be more simple to use the app to open your window for your first meal, then close it after your second meal? What you’re describing is basically 16:8, 2 meals no snacks, correct?
Zero does have the custom fast option if using the app gives you that structure you’re looking for. You input the amount of time you will be fasting for, but I don’t think you can save that preset unless you pay for premium and would have to input it in each time.