BAPI_MATERIAL_MAINTAINDATA_RT ZZFIELDS

Hello,

I am updating mara, marc append structure  zfields using BAPI_MATERIAL_MAINTAINDATA_RT.

I am using function value as 004. Value is not getting updated to material master.

function = '004'

material = matnr value

plant = plant value

field1 = value of z field.

Please help me in using field1 to update z fields.

Thanks