Complex sentence: The Mondial was the first Ferrari car where the entire engine/gearbox/rear suspension assembly was mounted on a detachable steel subframe, making engine removal for a major rebuild or cylinder head removal much easier than it was on previous models.
Split into simpler sentences: The Mondial was the first Ferrari car where the entire engine/gearbox/rear suspension assembly is on a detachable steel subframe. This design made engine removal for a major rebuild or cylinder head removal much easier than it was on previous models.