Sure, this should get you going do a SOAP ADMIN call via JSP in a Zimlet on the server side:
Code:
String adminuser = "adminuser@zimbra.my.org";
String adminpassword = "mypassword";
// Standard SOAP URL on the local host
String soapurl = "https://127.0.0.1/service/soap/";
// Admin SOAP URL on the local host
String adminsoapurl = "https://127.0.0.1:7071/service/admin/soap/";
// Authenticate as the admin user
SoapProvisioning sp = new SoapProvisioning();
sp.soapSetURI(adminsoapurl);
sp.soapAdminAuthenticate(adminuser,adminpassword);
SoapHttpTransport soapHttpTransport = new SoapHttpTransport(sp.soapGetURI());
soapHttpTransport.setAuthToken(sp.getAuthToken());
BTW: there are many examples of how to do the proxy call to an external service in the Zimlet code provided w/ Zimbra.