Totally nub question here, but how do I access the script once I extract it to the Zplugs folder? I didn’t see anything in the .pdf explaining how to enable it (looked in the plugins palette and didn’t see anything).
QuadQuick was written before plugins existed. That means that it does not go into your ZPlugs folder. Instead, it should go into your ZScripts folder. It then needs to be manually loaded via the ZScript palette.
This is a very old script, which I’ve never been able to find the time to update to ZBrush 2. I’d actually recommend that you use the Reference Image plugin by marcus_civis instead.
And I’d recommend you use Reference Image 2 instead. 
Although you can only work with one view visible there is an option to see a snapshot of all views. Give it a try.
Actually, try as I may, I can not find any difference between reference image 1 and 2 by reading the descriptions. They appear to do the same thing, the same way, with the same features. Or is there something I’m missing…
Reference Image 1 uses a single image which must contain all your various reference views (front, left, right and so on). The scale of those views is therefore limited by how they fit on that image and the maximum canvas size.
Reference Image 2 uses separate images which can all be at the maximum canvas size (if you wish).
That’s the main difference, which is largely one of convenience. Reference Image 2 has some extra features and extends features available in version 1. Which, if any, you prefer would depend on trying them to see which fitted best with your workflow.
Is there going to be a version of this for Z3 or is it built into the new version already? I figured they would have included this in the New Zbrush!
There isn’t even a version for Z2, specifically.
I figured they would have included this in the New Zbrush!
I think it was a concession for old-world 3D users. Sort of a step backwards from the artist-centric paradigm. There may be times where it speeds up workflow*, but for the most part, it’s neither efficient nor intuitive.
Plus, if you’re giving up 75% of your useable screen space, and probably tripling the overhead required to work with any given model, you’re really not taking advantage of what Z3 has to offer. 
*(it makes more sense for zspheres than pixols)