Here is a link to the 2012/2013 ish C Max - Engine choices are near the end.
Here is a link to similar Focus brochure. Engine choices also near the end.
You should be able to find your engine code on your V5 under engine number or variant. If not there it will be on the VIN plate or on the engine somewhere.
Google says the 1.6 Duratec is a Sigma engine. The Zetec was an earlier version of the Sigma. These engines are totally different to the higher powered Ecoboosts.