what is the difference between the pro's...
what is the difference between the pro's and the regular Z1's?
The Z1 Pro has a different sole. While they both have Vibram soles, the Pro sole provides better traction in and out of the water. The trade-off? The pro sole is a marking sole, meaning that it can leave marks on floors. Since it is softer, it can also wear down quicker than the regular sole.
If you aren't going to be going in and out of the water (or will be using the sandals just for hiking), then the regular Z1's should be fine. However, if you know that you are going to be wearing the shoes around rivers or other slick areas (or will be doing lots of scrambling over rocks), I'd go with the Pro (and, actually, I'd also consider the Z2 Pro, because that extra toe loop really adds to stability).