Hi John,
Glad you like the update!
There are literally thousands of tutorials on the web about texturing eyeballs. I dont think Ive ever done any texturing of eyes in Zbrush, at least not the iris part. The iris usually takes a lot of layers built up to get all the little tendril-y cones looking right, and to be honest, Photoshop has a more robust layer system than Zbrush. I might use Zbrush to paint in all the little veins on the cornea and then load whatever iris image I came up with in PS. This way you can avoid texture seams.
The question I always struggle with is whether to add the eye reflections in the texture or try to work out the shaders to take care of that. Id always prefer to let the shader handle it because its more realistic and will react to different lighting conditions, but its often hard to predict what will give you a nice hotspot reflection with placing lights etc.