I don't think you'll be able to use the zoning method for your plant situation. You've got too many cross contamination points.
You'll probably have to zone the travel area as high risk UNLESS you can sanitize wheels on fork lifts every time (which isn't going to get done no matter how hard you try)
I will suggest that you incorporate quat based dry sanitizer granules to your operational program.......as they burst from walking/forks etc they release the quat to instantly sanitize whatever they are in contact with
Assuming you do not have dedicated fork lifts for each side? How many people are travelling between buildings?