This iterates over the data elements of an MTensor to do an in-place conjugation:
MTensor T0; mcomplex* z; mint i, len; ... len = libData->MTensor_getFlattenedLength( T0); data = libData->MTensor_getRealData( T0); for (i = 0; i < len; i++) { mcimag(z[i]) = -mcimag(z[i]); }