Controlling zones on multiple keyboards from one keyboard ?

[Mark]

Hi All,
I currently use an A-30 midi controller with a Roland RS-9 keyboard as the
sound source. Each keyboard can play two zones. The RS-9 uses channel 1 and
2 while the A-30 uses channel 3 and 4 for a total of four channels; 4
zones. I am looking to upgrade the A-30 to a midi controller that can
handle 4 zones rather than 2 zones. This will give me 6 zones instead of 4
zones. Midi controller - 4 zones, RS-9 - 2 zones. The question I have is
: Can two of the four zones used by the proposed new midi controller
actually be used to control the two zones on the RS-9 ? Or is this
something that some controllers can do while the cheaper ones can't. Or is
it a function of what can be sent/received per channel or something like
that. I am in the process of reviewing and ultimately purchasing either a
new midi controller to replace my A-30 or another lightweight synth similar
to my RS-9 which can double as a midi controller easily. Thanks for any info
you can share.

[Progmatist]

The M-Audio Keystation Pro 88 controller will control 4 zones.