Sorry Flo I think I misinterpreted your original question. So if I understand you correctly, you want to match the entire contents of the "result" element, including all of its sub-elements in a single XPath match assertion. Is this correct?
If this is so, have you looked at the Contains assertion that can use a RegEx? If you definitely need to use an XPath assertion, you can use a RegEx match, if you right click in the response in the "Outline" view you can select the option "Add Assertion... > for Content matching RegEx". I know this is probably not an ideal solution, but it's the only one I can think of.