If you have now solved the problem by a rebuild, then mark it as solved so no one else spends too much time looking at it.
A short circuit with a 2 amp power supply would be difficult to ignore since this would usually be accompanied by heat and smoke. More plausible would be a polarity reversal on the jack plug combined with a user failure to notice the '-' sign when measuring the voltage. Fortunately the MKR Zero is well protected against abuse.