If you want to remove the Amsterdam London leg on the first ticket and London Amsterdam on the second ticket. From a rebooking perspective, you are will need to ask EB if they can do it. But it might not be so simple, as there can be married segments with the long haul, and they may have to have award availability on the long haul leg, etc. But only way to know is to call.

Don't just no-show for the two London legs, that would cause chaos for your travel plans.