The main issue in your code is the presence of ampersands &, which constitute command concatenation operators.

Usually escaping special characters (like ^&) is enough, but in this situation a pipe | is involved, which instantiates new cmd.exe instances for either side1, which then receive unescaped characters. For this reason, you need to establish ...

However, composing escape sequences depending on whether or not pipes are involved is quite nasty, but ...