Yes you can put your Amazon/eBay capsules at the same time. But make sure that the products don't violate Google AdSense program policies. For example, you are not allowed to write about prescription drugs, so don't put any products related to drugs.
As eBay/Amazon products and texts can be read by the AdSense bots, you might want to put some high paying keywords products in your capsules. For example, "Mesothelioma" in some products about cancer and asbestos!!