To change your Hosted Zimbra login password, please login to the Zimbra Webmail client at https://webmail.businessemail.net.au/ using your existing username and password.
Once logged in, select either Preferences (1) and Change Password (2), or the menu dropdown (A) and Change Password (B)
You will be presented with the change password screen. Enter your current password (1), then enter your new password twice to confirm(2). Once done, click change password (3) and log back in with your new password.