With the chest behind both machines, it can be ejected into by both. Ejector and Pulling upgrades are tried in order that they are in the upgrade slots, meaning you want an ejection upgrade pointing towards the Thermal Centrifuge first, that will export all the Purified Crushed Uranium Ore, and an ejection upgrade pointed towards the chest second to export everything else. A little like this:
Now in the Thermal Centrifuge, all you need is an ejection upgrade pointing towards the chest that will export everything it makes into it. The redstone inverter upgrade is optional, it allows it to stay warm without constantly needing an input.
Obviously the upgrade direction arrows will depend on the orientation of the machines, but the point is so long as you shift right-click them on the side you want to eject out of, this should work fine.