You can select multiple nodes in XPath, but you cannot re-arrange XML in the manner exhibited in your requested output.
Also note:
Your sample XML is not well-formed; it must have a single root
element.
You can indeed select multiple nodes as your title question asks
using the union operator | you suggest, however...
Your desired XML is not available for selection, which XPath
does, but it could be constructed via transformation, which XSLT does
(provided you're willing to wrap the desired XML in a single
enclosing root element).