Example on how to do this can be found here:
https://github.com/Legrandgroup/libezsp/blob/8571574085160bc71177f68795f09b17b3c2ad7f/example/mainEzspStateMachine.h#L105

Note you should check that the libezsp library exports its NSEZSP::CLibEzspState state as NSEZSP::CLibEzspState::READY before you invoke NSEZSP::CEzsp::getAdapterVersion() or you might get an empty or incomplete version returned.