Never owned a ZDZ-40, but have had a chance to take a good look at my buddy HT's motor. I did set the needles on it and point the tach. His turned a Mejzlik 20x10 at 7600 rpm. My Brison 2.4 would turn the same prop 7100 rpm. I have a Brison 3.2 and have put the tach on a couple of others. The best one turned a Mejzlik 22x10 at 7200 rpm. The "weaker" one turned it about 6900 rpm.

Haven't seen a ZDZ-50 yet.....too new.
But, considering that the 40cc motor is stronger than the Brison by a healthy margin, I'd be surprised if the ZDZ-50 also wasn't stronger than any of the Sachs-based 3.2 motors. In the HP/$ war, I think ZDZ has 'em beat.

The Brison 3.2 is a good little motor, maybe the best for power/weight of their line. The only trouble is that the design is getting a little old and the competition keeps pushing forward.