With newer Motorolas, you can put more than 16 channels into a "zone", and program soft menu keys for CHUP and CHDN, then use the up down channel buttons to scroll through a huge list of channels (until you reach the channels per zone limit) that extends past the 16 channel knob selector. This is great for dumping, say like a huge list of wildland brush fire tac channels into a large pool instead of taking up 5 zones for the same pool of seldom used channels.
For APX there is also an enhanced zone bank option, that turns the ABC switch into a quick access selector. I have only played with it on someone elses APX, but it seems like when you activate this, it uses the zone you are currently on as the master, and when you move the ABC switch it will move you up through the next three zones?
Paul