Hi Fernando,
KNA1-JMZAH is related to employee, rather number of yearly employees. I doubt there is any field in CRM related to this field. What kind of information is stored here?
See below thread. They may be useful if you have not seen them already
Mapping of Fields between CRM and ECC
BP replicaation from ERP to crm
Besides there could be Notes available on mapping.
Cheers,
Niraj