I can see z3ta+2 in my products page as registered but not in command centre so it's impossible to get the latest update.
 
any ideas ?

The original z3ta+ does not have a Command Center compatible installer, z3ta+2 does.
Looking in my account, v1.5.3 appears to be the last release not bundled with SONAR. This version is also available from the knowledge base. If you have SONAR Professional or Platinum there is a newer release, now called z3ta+ classic. I only know the Platinum installers. In Platinum the most recent z3ta+ classic is in the "Platinum Instrument Collection."

 
Cheers, edited to +2 I have Z3ta+2 in my account but not showing in command center.

Z3TA+ 28/4/2012CWZ32**********9F77C**********

Contact Cakewalk Account Support.
There should be an entry for z3ta+2.2. It has a different serial number and Command Center compatible installer.

I have, cheers. lets see ;-)