The RE0s seemed dryer in the mids to me and the ZEROs more forward and fluid in the mids.
The lows to me seemed pretty similar, both responded to EQ in the Lows.
The RE0s extend higher, but could seem quite harsh to me at times.
The ZEROs handles the highs nicely though.
The magic is in the mids for the ZEROs.
As far as detail, the RE0s may seem to have more detail in its extended highs, but because of the more forward mids of the ZEROs I felt the ZEROs...