Z3ta+2 vs synthmaster

They both have demos. Why not try both out and see which one works better for you?

Synthmaster is a great choice for sonic versatility, but for ease of programming it's only slightly more intuitive than Z3ta.
 
All modern soft synths, IMO, are severely UI-challenged. What you have to do is pick a synth based on what you've heard other people do with it, on the assumption that if they could figure it out so can you.
 
(btw, after an arduous selection process I chose U-He Zebra as my own primary synthesizer, but Synthmaster was a close first runner-up.)

I have both and if I were forced to give up one of them, I'd pick Z3ta without a moment's hesitation as the one to part with.  Z3ta does have a few competencies that SM doesn't: wave shapers and daisy-chained oscillators.  But SM is one of the most versatile synths I've yet encountered.  I found the factory content to be a mixed bag, but there are a nice number of add-on sound sets (for about $15 apiece) that bring something special to the table.  Z3ta has nothing comparable, IMO.
 
Oddly enough, I find Z3ta's user interface a bit easier to comprehend, and I'm not just talking about esthetic issues like color.  But SM has reasonably good documentation and with a little effort you can master it without a huge educational effort.  But it is a somewhat more complex instrument than Z3ta, so it will have a correspondingly longer learning curve.