Using A Rotary Control across split zones

[Corrençois]

I'm a newbie to the RD2000 so perhaps someone can help me. I've set up two TW organ tones split into two zones (to have an upper and lower manual) and I have a foot switch to control the rotary effect plugged into FC1. I want to have a single rotary effect controlling both zones. The problem is that the FC only seems to have an effect on the currently selected zone - even though they are both set up to receive tremolo rate commands via FC1. What am I missing? Is is not possible to control two zone effects at once or to route two zones through the same effect?