Which ZED agreements apply is dependant upon which airline you work for. Airlines form agreements between each other and decide if they are going to offer rebates at 90%, 75% or if they are going to subscribe to the ZED rules.
You will need to contact your own airline Staff Travel office ( Pass Bureau ) to determine your agreements however as you are with Delta I think the answer is probably none as I don't believe Delta have signed up to the ZED charter as yet.