This has been well discussed or argued on the gearslutz recording/mixing forum and after reading 26 pages here is what I found:
1) One person tried them and found that it made a significant improvement for their mixing/recording in a somewhat small room, which many of us have and he had used common brands (GIK) or made his own. Can't qualify how well the previous treatment was implemented and he couldn't figure out how to make REW work on his Macbook so no measurements. But - this seems like Cellcbern's experience. What's worth noting is that both agreed it improved their bass response.
2) One person thought it was good, improved imaging and soundstage, but didn't address his low frequencies issues enough and had some poor customer service due to damaged shipping. He did take some measurements but didn't publish anything either below or above 200hz (I can't remember which it was) and it showed some improvement but not tremendous or perfect in any sense. Mainly he criticized the customer service aspect.
3) An acoustical studio designer/contractor (a critic of ZR on that thread) said he visited one or some of the Universal Studios that had ZR rooms and said the ZR panels claims had no "substance" but never commented if he thought the rooms sounded good or not.
4) In contrast, another engineer/mixer (not of fame) visited the same rooms and said they were quite remarkable. He also commented that the room construction was not anything special, even for studios. That the rooms were like what you would have in a typical house/office with regular drywall. No double walls constructions and what not.
4) Among the many, two of the people arguing against, both own acoustic treatment companies - GIK and RealTraps, were arguing on the basis of physics, inaccurate use of the term "quantum" and the need for measurements, which is a valid point and I understand the need for most people to have measured evidence for any performance claims or in this case, they only look at the data.
5) The main argument for ZR: why would major studios and recording engineers with some serious resumes vouch for ZR and say that it sounds great and it does what Hsu claims in does, as in the interview with Warren Huart, a well respected producer/engineer. More natural sounding, better imaging, huge sweet spot in the room if the not the entire room, and when played back in the mixing studio, it sounds just like the way it does in the recording studio.
So my guess at following possibilities:
1) ZR and Hsu are complete frauds and selling snake oil. For over a decade.
Then they would have fooled some of the best in the recording industry. If he was a total fraud, why was he not sued or ran out of town? Could he have fooled that many people? What is the possibility of this happening in the recording industry?
2) Hsu stumbled upon something he really doesn't understand but for some reason it works so they try to market it and make it seem magical.
It would be amazing if this were the case and we can happily benefit from it.
3) It works to a certain degree but really nothing more that fancy wood panels with intricate carving that reflect/diffuse possibly some sound.
That the same results or better can be achieve with traditional treatment.
That would be unfortunate but true of many "miracle products".
4) The physics says that being 3/4" thick, it can't possibly effect anything below 200hz, but does do something special to the frequencies above.
Not a bad compromise if it works in conjunction to bass traps/absorbers. However, how do you explain reports (as in the Warren Huart interview) from people who have been in the room and say there's no corner bass buildup and that it sound the same pretty much anywhere they went in the room with great neutrality and imaging? It's possible they're being fooled somehow which is quite impressive.
Personally, I would love for this product to work, as in not needing bulky bass traps in the room with my low frequency issues. If I take measurements before and after and report no significant measurement differences but significant hearing differences then I would be at least happy with sound, whether the data confirms it or not. My optimism may cost me a good chunk of change but I've wasted more money on worse things and at least I can report back here for others.