Does the zbrush disk give me zbrush or what?
I assume you’re referring to this: http://store.pixologic.com/ZBrush-4R6-Backup-Disc.html
It is strictly a backup copy of the installer. It is completely useless without a license because purchasing the license is what gives you the serial number that is necessary for activation.
Basically, the disk option is available separately from ZBrush itself because some people decide after purchasing that they wish they’d ordered a backup CD. But buying the disk without also buying (or having bought) a license won’t do you any good.