I have both z3ta+ and Vanguard, and trust me, z3ta+ beats it by a landslide. To start with, z3ta+ has WAY more presets than Vanguard, and not only that, but the all sound much better than Vanguard's. Secondly, z3ta+ has much much more capabilities than Vanguard and what you can do with Vanguard can surely be done quicker and better on z2ta+. Finally, Vanguard's window is way too big... :P
Still, Vanguard is MUCH simpler, and if you don't like long and tedious trial and improvement to find out how to make sounds, then z3ta+ isn't for you.