how can the current flow if the potential difference is 0 volts?
This is one of those situations where &quot;ideal model&quot; and &quot;real physical system&quot; differ; all real physical conductors (except superconductors, which are weird) have ohmic properties and a non-zero resistance. So the voltage won't be zero, it'll be nearly zero.
Educational models and many simulators round &quot;nearly zero&quot; to zero to reduce clutter.