I'm NOT a racer, just a hobby/health rider; not competitive.
I bought a pair of the Zxellium Ultimates a few months back and really like those shoes a lot. Those are all black, causing me to worry about heat in the summer months.
I spotted some of the white/black Pro's on BT for under a bill and figured I get a backup/summer pair of shoes. I can't believe the quality of shoe for the price.
There's only a hand full of differences that I can see between the Pro Road and the Zxellium Ultimates.
1) The Pro's don't have a shoe bag... no big deal.
2) The Pro's have a normal detached tongue (like most tennis shoes), and the Zxellium Ultimate's tongue is only detached on one side; the end result is that Pro is easier to get on and off IMO.
3) The material seems a little harder or more plastic like on the Zxellium.
4) The strap nearest the toe does not have as much adjustability in the Pro model as the Zx Ult.
5) A HUGE weight difference of, get ready: 7-8 grams per shoe with full hardware installed (by my scale).
If someone was deciding between the ZX, ZX Ultimate, or the Pro Road, I would get the Pro Road hands down. That is, unless that someone is a racer and real competitive; I don't know how important the 16 grams would be.