It is geared to a younger customer, more fashion forward, trimmer fits, etc. It is made in a Zegna factory located in Mexico, but it's also about a third less than the mainline ($995 - $1200 for a suit compared to $3000 for EZ). It's not a question of comparison, but what you are looking for in terms of fit and style. You will find a lot of similarities in fabrics because both lines are made with Zegna's own fabrics. They take more risk with fabric composition in the Z line.
As for fit, the jackets have a higher armhole, suppressed waist, and are cut shorter. There are two styles, City fit and Drop 8, with the latter being the slimmest of the two. The City Fit is in between the mainline and Drop 8 in regards to fit. All of the pants are flat front.