SAP PO: File to REST scenario zip all files

Hi experts,

I am working on PO 7.5. My scenario is File to REST and the requirement is I need to zip three files A, B and C. Where the files B and C should static(pass through) while the file A should go through mapping. The resultant of file A is an XML format. All the three files A(After Mapping),B & C should be zipped together and sent to REST API. So, could anyone suggest the best approach to design the interface? Thanks all.