I think your limited to 2 speakers per talk back zone
So you can have a 6 zone v-2006 ahf and have 6 zones of talkback but all call page is 1 way only
as you asked.

I used 4 zones out of 6 ,but customer uses all
call for every page.

Talkback on all those zones just wont happen

Valcom 1-800-825-2661 for tech support