The Zoom Fly is the training half of Nike's carbon-plated range. It carries the plate and the ZoomX foam of a racer but with more durable materials and more shoe under you, at an 8 mm drop and roughly 265 g. Wear it for tempo runs, long runs with quality in them, and the races you do not want to spend a pair of Vaporflys on.
It is heavier and less lively than a true racer. If you are chasing a time on a flat course, the racer is faster.
It is not an easy-day shoe. The plate feels stiff at slow paces, so keep a normal trainer for recovery miles and bring this one out when the session has a target.