Alas, no. The dirty little truth is that damned near anything will cut glass. Go outside, pick up the first pebble or rock you see, and you can see for yourself.
See, the information doesn't come from what the gem will do to the glass, it comes from what happens to the gem when you cut glass with it. When you take a faceted gem and scratch glass with it, the scratching creates a gouge in the glass along with a little debris field of microscopic bits of glass that grind back against the object doing the scratching. A diamond is extremely hard, and will be unfazed by this retrogrinding. But if you look through a loupe (and sometimes even the unaided eye) at the facet point of a softer gem used to scratch the glass, you'll see that the facet point has probably been damaged. So the scratch test won't tell you that something IS a diamond, but in many cases it will tell you what is NOT.
Note:
CZ has a mohs hardness of about 8, while diamond is 10. Window glass is about 5, and quartz is about 7.
http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
PS:
I doubt that a fine gem would have been mounted in that ring, but it is a remarkably attractive stone. It might be a zircon which is a semiprecious stone that comes in a wide variety of colors, including yellow, and takes a nice facet.