Using 4 mono blocks

Please elucidate...

infection, one way to do this using the existing in-speaker x-over is:
* use a y-connector on preamp L ch
* connect one output to 1 mono driving the mid/hi
* connect 2nd output to 2nd mono driving the bass/mid-bass
* use a y-connector on preamp R ch
* repeat connection hook-up using mono3 & mono4. 

each signal going into the Zodiac will be 20Hz-20KHz but the in-speaker x-over will filter the input & pass on the required signal bandwidth to the appropriate drivers. 

Just looking at the Zodiac from a side-view photo, it looks like they have 4 pairs of speaker binding posts. So, one could have
* 1 speaker cable pair driving the bass
* a 2nd speaker cable pair driving the mid-bass
* a 3nd speaker cable pair driving the mids
* a 4rd speaker cable pair driving the highs

Needless to say, at $127K per pair, it's a cost-no-object speaker & getting 4 speaker cable pairs would not dent that buyer's wallet.  

Thanks bombaywalla.

Can you recommend a high quality Y connector? 

Just realised I should mention that I asked this question because I have only 1 pair of outputs  (XP-20).
I know it would be a no-brainer if I had 2 pairs...

For splitting RCA outputs I’ve used this Audioquest "hard y-adapter" with good results. However since the XP-20 provides two pairs of RCA outputs but only one pair of XLR outputs I presume you are referring to XLR y-adapters. While there could very well be others, the only XLR y-adapters I am aware of are those made for the pro audio market, such as the ones shown here.

Also, a point to keep in mind is that the output impedance of the XP-20’s balanced outputs is somewhat high, spec’d at 1K, and perhaps higher than that at some frequencies. And if you connect each channel to two identical monoblocks it would see a load impedance equal to half the input impedance of either amp, which could result in an impedance incompatibility depending on the input impedance of the amp and on how the XP-20’s output impedance varies over the frequency range.

Another point to keep in mind is that the output of the preamp for each channel would see the total of the capacitances of all of the interconnects that are in the path to the two monoblocks for that channel. Given the somewhat high 1K output impedance, if the cables are particularly long and/or do not have low capacitance per unit length the result could be a perceptible degree of rolloff of the upper treble.

In the case of many preamps, btw, both of those issues could arise EVEN IF the preamp provides two pairs of outputs. As most preamps providing two pairs of outputs do not drive them from separate output stages, but simply jumper them together just inside the rear panel. Which from an electrical circuit standpoint is no different than using a splitter externally. (And may even be worse than using a splitter externally, if the amps are positioned such that the split can be done near their inputs, with most of the distance to the preamp being handled by a single cable rather than by two cables). Although the two pairs of RCA outputs provided by the XP20 have a considerably lower impedance (150 ohms) than the balanced outputs (1K), which would lessen both concerns considerably. While nevertheless probably sounding worse than balanced connections if you are using a balanced Pass amp, or some other balanced amp.

Good luck. Regards,
-- Al