How to Power a New Layout

Very close - you are thinking in the right direction.  Use the (2) ZW's,  using the AU and DU circuits on each transformer for the trains, and leave the the BU and CU circuits unused. This will give you dedicated power with whistle/horn control for all loops, without accessory operation(s) affected by the train load, and will eliminate accidental "nudging" or creeping of the B-U & C-U dials from being a worry.

Your KW's are key. Although the fixed 20 volts is really not much use, the fixed 14 volts makes a good circuit for illuminated accessories that don't need dimming(this would have to be a dedicated circuit, though, because the KW 14 volts does not share the common ground "U" w/ A & B).

That leaves you with two variable circuits, "A" & "B", that can be phased to the ZWs for track/train activated accessories and fixed voltage switch/turnout power that require occasional fine-tuning. Add another phased KW in and you have 4 total variable circuits to work with - a good size layout with many 022 type switches and controllers will approach the output capacity of one KW when you start adding up all of the bulbs, while leaving some overhead to activates the switch coils.

Distributing the whole load over 4 or so good transformers sounds like a good solution for what you have proposed.

Jim, your 2 ZWs will be ideal for controlling four tracks.  The A and B with U posts on the KWs can be used for lighting and accessories.  With that combination your can vary the voltage to all outputs.  For "best practice" be sure all transformers a phased and each individual variable voltage output circuit is protected.  The lighting on a layout is the biggest load.

The transformer chart at the bottom of this Phasing page shows transformer circuitry for phasing purposes.

Personally I agree with the friend and would use the two ZWs for railpower and the KWs for lighting/accessories. 

Are you contemplating 4 separate power districts, each powered by an A or D throttle with the max output of about 190 watts per ZW available for the two districts? If you run any long incandescent-lighted passenger consists having ample railpower is good.

You probably already know the following___but the ZWs used for railpower should be phased and crossovers between power districts should have an insulated pin or a gap in the center rail between the switches. A single "layout common" from the ZWs is all thats necessary.

When crossing over between power districts you should try to equalize the voltage of the two controlling throttles since the first engine pickup will be in the leading district and the other in the trailing district--straddling the gap. [if Command Control at fixed 18 volts throughout it makes no difference].

Sorry I type slowly and didn't see Susan's post.