Yip,
Had this when installing Z3TA+ 2 last night vis CCC. I too had Z3TA+ 2 pre CCC days. CCC did not find the previous install nor update it.
Via CCC it installs itself in the cakewalk content folder and the VST64 bit folder that you might have set in preferences in CCC.
I did notice that after doing a CCC install of anything it does download the install files first to a folder on your PC that again is setup in CCC preferences. Sets up a cakewalk folder there. After using CCC it does not clean this up so all the install files are there if you need them in the future :D
A round about way would be to install via CCC. Grab the install file from that folder. Uninstall Z3TA and install again via that installer which is the normal installer asking you where you want it installed, unlike CCC.
I also dont find Z3TA+ 2 to be the most portable of VSTi instruments as it does seem to need bits installed in PROGRAM FILES Folder as well as in your VST64 Bit folder and maybe the cakewalk content folder.