Facebook passes fbclid parameter automatically in all links that are being clicked on Facebook, therefore you only need to create a parameter on the Zeustrack side, to store the data passed by Facebook.
Go to your Facebook Traffic Source template in Zeustrack and create a custom variable as shown on the screenshot. Leave the Placeholder column empty and only fill in Parameter and Name columns.
You may then pass fbclid to your offer page by including {var1} parameter in your offer URL.
Before placing the Money Page URL in a Facebook ad, be sure to remove &fbclid=
from the URL. Part of the fbclid parameter values will be lost without this action.