Sonar Studio X2A Z3TA+ 1

It is not possible Z3TA+ Classic is not multitimbral.

If you are trying to have a single instance of it play a different sound on different midi channels at the same time, it will not work, because it does not have that functionality in it.
 
You could simply add an additional instance of it to the synth rack, and load up a different sound, along with its own audio and midi tracks.  You could do that for however many different sounds you wanted to hear from that synth.  Folks do this all the time with synths that only allow a single sound to play at a time.
 
And the other poster is also correct, in that you could send program change messages as midi data, BUT I think it is generally better to keep each sound intact for a given track.  
 
It is my opinion that there is too much potential for trouble if you have to deal with multiple program changes for a given synth instance on a single midi track.  (it gets confusing, the effects get too complicated, as does mixing, when trying to process different sounds in the same track).
 
So, I routinely may have 2-3 instances of Dim Pro or one of the other synths, each with a single sound loaded, and all routed to their own audio and midi tracks.  It just keeps it all simple.  (Yes, I know Dim Pro can play 4 sounds, I just don't bother with that - though for Kontakt 5 I routinely load up 5 or 6 instruments in a single instance).
 
Anyways, try just loading up an additional instance of Z3ta+1, and see if that fits your needs.
 
Bob Bone