Most sites I find tell me how to distinguish the neutral wire from the live wire. Basically, you find the one that has current and the other one is neutral. That's all fine and dandy when you only have 2 wires. What if there are three or more? Sure it's usually the white one, but when 3-way and 4-way switches are concerned or if you just don't trust the previous electrician, how can I be sure that a particular wire is truly neutral and not just a traveller, for example.
For example in the following image, the neutral wire ends at the light fixture and for the sake of newer Z-Wave switches neither of those switch boxes has a neutral wire. So if I open a box and see a bunch of wires apart from identifying which one is live, how can I verify without a shadow of a doubt which of the others is truly neutral if there even is one?
Please don't assume this is the wiring I have. This is only an example to help clarify what I am asking.
Furthermore, if any particular wire is indistinguishable from neutral, then why does it matter which one I connect to the Z-wave neutral terminal. I know it does matter.