Lube everything! Oil and especially clean out old grease before it grinds up a gearset. (Old grease hardens, chunks into grit & will do damage)..Lots of lube choice and cleaning threads.(motor oil is ok for now) NOT WD40, you may clean grease and stuff with it but it is not a suitable lubricant here.
To use two ZWs together safely you also must phase them together to avoid overvoltage (like double it) and some other issues.
There is a Lionel made video on "phasing two or more trasformers to be used together" I suggest watching. It is pretty informative about about the whole process of changing wall plug AC to low volt, and ac cycling, etc.. Not too long and just involved enough to "really get it" on ac vs dc . (Even if you don't use both, you will learn and brush up, Mike is easy to listen to imo.)
There are also quick and easy approaches and higher tech ways of checking. You could just learn the easy way (both shown) but you won't learn why you are doing it.
You need a low volt range meter for it to be worth it. Don't bother with a 120v meter for use with our usual 5-25v. I look for a 25-50v face
Put transformers on a power strip that has a breaker.
Internal breaker is really for the transformer. So fuse or breakers as noted on outputs, and with ZWs I'd stick to 12g stranded wire to amp meter, then again to the track, or as a "bus wire" to multiple 14g drops from track. (1 long & fat to feed multiple short & thinner wires; for best distribution)
Clean the old track well, consider new. It really does make things run better.
Please read up on a few modern choices here before you buy. In fact, ask about everything & talk about everything. It will save you from yourself even when you're sure your right 
