I've taken a look at the SOAP interface with an eye to putting together an alternate SOAP server to talk to my existing mail/calendar store.
From what I see from protocol traces (?debug=3), the ZCS submits using something akin to a SOAP package (the attributes on a SOAP Request seem strange to me, and I haven't figured out how to handle them yet), but the return value is not SOAP - it's JSON (very different format).
Questions for the developers:
1) Does the ZimbraWebClient only accept JSON, or will it accept return values that are true SOAP?
2) What versions of the SOAP standard do you implement?
3) Do you have XSD files for the XML submissions?
4) Do you have WSDL files for the SOAP calls you do make?
Thanks in advance,