If you have a ton of it to 'unzip' there is a special tool you can order. Otherwise, an old hockey stick works great. Pull up a tile or 2 on the line you want to unzip, slide the hockey stick in, slide it along the seam, keeping it mostly flat. Should unzip easily once you get the hang of it.
I've done tens of 1000's of square feet of the stuff as sportcourt for a traveling show. We never unzipped it smaller than 4 ft square pieces. We had a special cart that it stacked onto. After a while, you learned how to pull up and sort of snap your wrists to pop it loose along the seam (and after hundreds of cycles, it gets a lot easier to unsnap.)
zuk