I'm doing some testing with the zabbix API, but we've got all of our user accounts in LDAP.
I've been blocked by getting a successful authentication, until today when I tried the default Admin account.
Using the Admin account to access the API works fine, while using any LDAP-stored account fails with the message:
Error -32602: Invalid params., Login name or password is incorrect
In api/classes/class.cuser.php, it looks like the authenticate() function is hard-set to use ZBX_AUTH_INTERNAL. This should be looking up the auth settings from the database, and attempting to authenticate using LDAP, if it's configured.