Wiring a ZW transformer is simplicity itself. There are four pairs of connecting posts on the back, one pair for each of the four variable voltage taps. Each pair has common on top and the hot lead below. The pairs are arranged in sequence to match the taps themselves, say A, B, C, and D, with A and D being the large-handled taps on each end of the transformer, and B and C being the small-handled taps on the inside. Unlike some other Lionel transformers, each tap is capable of the full range of 0 to 20 Volts AC.
Each post is a round knurled nut on a stud. I use 18-gage wire as the leads to the layout to carry the considerable current they draw. (You can use 24-gage for lights, but I wouldn't on the transformer itself). Strip 3/8 inch off a wire and wrap it around the corresponding stud, or use a spade connector. Tighten each wire with the round knurled nut, and move on to the next wire. Whatever you do, don't allow the wires or the connectors to touch each other, or you'll have a short right at the transformer itself!
The ZW has a red light that comes on in case of overload, which is a great feature if you have young children. They can - and do - learn to turn it off if that light comes on.
If that light comes on without derailments, then you are overdriving the transformer, and you will need to get more transformers to power your layout.
Can’t help you with Powerhouses, TPC 400, or TMCC. Just guessing, but you might be able to order manuals for these (if they are Lionel products) from Lionel itself.
Lastly, did a quick look at the http://www.ogaugerr.com
forum, subcategory “On Amps, Watts, and Transformer loads,” and their voltage calculations appear to be incorrect. (Once at the web site, click on "OGR Forum"). A ZW transformer draws 275 watts from your house, regardless of the number of trains you have, and regardless of the voltage you apply to the track and accessories. At 20 volts, you’ll get up to
13 amps or so (275/20 with rounding off and line losses) applied to the track and accessories. At 10 volts, you’ll get up to some 6.5 amps. This is so because the load current (the current capable of being applied to your track and accessories) is proportional to the voltage applied: load current = voltage applied divided by resistance. The resistance goes down for each train or accessory you add and operate, and the current goes up. And to get that 13 amps or so, you would have to hook a lot of equipment up and power them all - one train with lighted passenger cars, say a Santa Fe A-A dual-motor set with three twin lamp passenger cars, would not draw 13 amps. A ZW should be able to handle four trains such as that.