join data by position of different json elements on dataweave 2.0

Something like this should work

%dw 2.0output application/jsonvar filteredExport = (payload.Z_HYD_GET_INVOICES."export") filterObject ($$ ~= "ACCOUNTING" or $$ ~= "FISCAL")var filteredExportArray = filteredExport pluck $var accounting = filteredExport.ACCOUNTING pluck $var fiscal = filteredExport.FISCAL pluck $---{    invoices: filteredExportArray map {        accounting: {            accountingDocumentID: accounting[$$].DOCNUM,            taxEntryDate: accounting[$$].PSTDAT,            company: accounting[$$].BUKRS        },        fiscal: {            fiscalDocument: {                fiscalDocumentID: fiscal[$$].DOC_DOCNUM,                fiscalDocumentCategory: if(!isEmpty(fiscal[$$].DOC_NFTYPE)) fiscal[$$].DOC_NFTYPE else if(!isEmpty(fiscal[$$].DOC_INVTYPE)) fiscal[$$].DOC_INVTYPE else null            }        }    }}

You could also use a join function on the two arrays as you mentioned you'd like to see

%dw 2.0import * from dw::core::Arraysoutput application/jsonvar filteredExport = (payload.Z_HYD_GET_INVOICES."export") filterObject ($$ ~= "ACCOUNTING" or $$ ~= "FISCAL")var accounting = filteredExport.ACCOUNTING pluck $var fiscal = filteredExport.FISCAL pluck $var joined = leftJoin(accounting, fiscal, (a) -> a.DOCNUM, (f) -> f.DOC_DOCNUM)---{    invoices: joined map {        accounting: {            accountingDocumentID: $.l.DOCNUM,            taxEntryDate: $.l.PSTDAT,            company: $.l.BUKRS        },        fiscal: {            fiscalDocument: {                fiscalDocumentID: $.r.DOC_DOCNUM,                fiscalDocumentCategory: $.r.DOC_NFTYPE            }        }    }}

Give this a shot.

%dw 2.0output application/jsonfun returnFiscalDoc (docnum) = {    fiscalDocument : {(payload.Z_HYD_GET_INVOICES.export.FISCAL.*row filter ($.DOC_DOCNUM ~= docnum) map  {        fiscalDocumentID: $.DOC_DOCNUM,        fiscalDocumentCategory: $.DOC_NFTYPE default $.DOC_INVTYPE    })}}---invoices: payload.Z_HYD_GET_INVOICES.export.ACCOUNTING.*row map {   accounting :      {         accountingDocumentID: $.DOCNUM,         taxEntryDate: $.PSTDAT,         company:$.BUKRS     },   fiscal: returnFiscalDoc($.DOCNUM)}

Though keep in mind your data under FISCA.row has DOC_NFTYPE and DOC_INVTYPE. Thus used default in the function above to get to the value of the required.

"FISCAL": {                "row": {                    "DOC_DOCNUM": "0002990790",                    "DOC_NFTYPE": "ZW"                },                "row": {                    "DOC_DOCNUM": "0003006170",                    "DOC_INVTYPE": "ZW"                }            }