But regardless of whether the zipper car is on the right or the left side, once I put them together at the bottom, I always use my right hand to raise or lower the zipper. I think this would be true regardless of whether the zipper raiser was right- or left-handed.

It is possible that if, in the design of the product, the flap overlaps toward the left, that would be more convenient for the left-handed person, and if the flap overlaps to the right, it might be better for the right-handed person.

But let's just disregard the direction of the flap for now and concentrate on the design of the zipper itself. I'm sure we can save the flap issue for a later thread.