Many Campervans and Motorhomes have furnitures protruding into the sliding door areas.
This can be ie a kitchen cabinet or seats, some of this furnitures even have a table which can fold to the outside of the van when the door is open, or a seat/ bench has a door which opens to the outside when vehicle door is open.
In this above samples, a 3 zip version screen is most likely a good idea. It helps to reach from inside 2 out of the 3 zips for opening and closing. The 3th zip is then operated from the outside only to give access to doors and tables OR to have the steam and fat of cooking to escape easy to outside and not catching into the screen.
If your cooker/ stove is in the protruding part of cabinetry in the sliding door area, we recommend definite a 3 zip version.
If a small off centre opening is your choice- make sure to measure the free non obstructed distance, subtract approx 5cm (2 inches) and then choose or order a appropriate 2 zipper screen to make sure that you can reach both zips when you are inside your van.