I'm inclined to believe we should avoid using the term "over unity" in describing ZPE devices, for two reasons. Firstly, a ZPE device is no more an "over unity" device than a windmill, and secondly, those of us advocating The Disclosure Project have already raised enough eyebrows with references to extraterrestrial visitation, reverse-engineering and the like without throwing a term like "over unity" into the mix.
Getting back to the windmill analogy - I trust you'll agree a wind generator is powered by ambient (wind) energy with an efficiency clearly less than unity. Energy input and output are readily measured and compared, so this is hardly controversial.
Just as the windmill is powered by ambient wind energy, the ZPE device is powered by ambient (in this case ZP) energy. The key difference here is that unlike the readily-measurable wind energy input, we're dealing with an ambient energy input which is far more difficult to quantify. Here we have a device which appears to be powered by nothing more than maybe a D cell battery (the remainder being ZP energy), and yet, as if by majic, we may get a few Kw out the other end. Hmmmmmm.
But let's not kid ourselves (or anyone else) about this being "over unity", as this would be a great disservice to what I sincerely believe to be the most promising new technology going. At this point I must confess to being a biologist (read "non-physicist"), so I hope you'll indulge me here. I submit the above in deference to others capable of doing math with their shoes on.