Packaging of XML and 1 or more PDF in one file

For transfer between custom solutions, the found sets in several related tables are packaged in XML.
Then, 1 or more PDF need to be added. I am adding them encoded and wrapped in [CDATA tags.
It works well and importing runs smoothly.

However, there may be a better solution to this. How would you package the XML and PDFs for transfer?

how about a zip file?

Or with DynaPDF put them as embedded files in the PDF.

Having the PDF embedded Base64 encoded inside the XML-string is the method of choice for electronic invoicing with Swiss Health System where the medical prescription needs to be part of the invoice.

tend to do it this way too

Thank you @MonkeybreadSoftware, @EfficientBizz and @harvest for feedback.