Zentail gives you the ability to select which sales channel a given SKU is listed to. Here's how:
Go to the Catalog => Search for and click a specific SKU
On the SKU overview that appears on the left side of the page => Scroll down to the "Channels" section.
Toggle to "List" to any channel you want to sell that SKU on. If there is no toggle button, you will need to resolve the critical issues listed for each channel.