Welcome, Dundy!
My first suggestion is to do a thorough inspection of the ZWs. THIS IS THE MOST IMPORTANT STEP! Most transformers of that age need a little TLC, or at the very least a good visual inspection of the power cord, internal rollers, and internal circuit breaker testing. With a faulty (cracked) power cord and/or faulty breaker, the risk of a fire is real. If the rollers are bad, you can do permanent damage to the coil windings of the transformer. If you are not comfortable with making the repairs yourself, it is worth every penny to have a trusted repair guy do the work.
A gentleman named, Kent S has a wonderful website with a very detailed walk-through of the inspection process (and repairs if needed) for a ZW. Click this link to go to his webpage: http://www.tranz4mr.com/ZW_Checkout.html
I'll second Gilly's advice on the meter wiring above.
The transformer's internal breaker is to protect the transformer, and not necessarily the wiring or trains on the track. That can be accomplished though - the best practice is to also install a circuit breaker in-line with the power to the track. Will you be running conventional postwar trains or more modern trains with command control? Modern trains that have sensitive electronics (circuit boards) also require TVS (transient voltage suppression) diodes installed between the common terminal and the hot/power terminals.
