Quite possible, yes. But the alternatives to zugferd look quite similar, due to requirements from the relevant laws:
https://de.wikipedia.org/wiki/Elektronische_Rechnung
translated excerpt:
an electronic invoice must be [...]
3. human readable
4. origin of the invoice must be guaranteed (digital signature or internal controls)
5. integrity of the invoice must be guaranteed
[...]
This means that while you might be able to use something other than PDF for the human-readable part, I don't think anything other than PDF will be used. All the other stuff (XML with embedded SVG or PNG, Word, plaintext) will have acceptance problems in one form or the other.
EDI is big business to big business, as evidenced by you mentioning SAP. There, you may be completely right, I don't know.
This means that while you might be able to use something other than PDF for the human-readable part, I don't think anything other than PDF will be used. All the other stuff (XML with embedded SVG or PNG, Word, plaintext) will have acceptance problems in one form or the other.
EDI is big business to big business, as evidenced by you mentioning SAP. There, you may be completely right, I don't know.