A zone block in football is a blocking technique in which the positioning of the offensive linemen is more important than the individual strength of winning a 1 on 1 and pushing the defender back. Offensive linemen are each assigned an area to guard rather than one individual defender, and defenders are often double-teamed with this strategy. A zone blocking scheme requires a lot of coordination as one mistake can mess up the entire play for the offense. The entire offensive line must be able to communicate what is going on in order for it to work.
Zone blocking is different within the passing game and the running game. In a running situation, the offensive line attempts to push forward and move the defense back so the running back can gain more yards. In the passing situations, the offensive line stays in their assigned area and picks up defenders that are rushing there.
The graphic below shows a running zone blocking scheme. The offensive lineman pushes forward and then blocks whichever defender is in their area.
When watching a zone blocking scheme, look at how the offensive line is moving their feet. Foot movement is imperative to the success of the strategy. In the event a tackle needs to 'pull,' they need to do so quickly, because if they do not, their zone is going to be overrun by the defense.
Zone blocking schemes are often used when a player on the defensive line is playing too well to be stopped by just one offensive linemen. With a zone blocking scheme offensive linemen can shift over to help out and double team a player if they need to.
The strategy behind zone blocking is that it is simplistic. When facing a defense that runs stunts and has a complex blitz, a zone defense is a way to simplify things. An offensive lineman does not need to worry about staying with the person they need to be blocking; they can just occupy a space.
The obvious difference between the two is that man blocking is blocking a specific defensive player while zone is marking a space. In terms of the difference in success, it varies from team to team and running back to running back.
Different coaches add their own individual touches on each scheme so the level of success varies depending on what adjustments are made. The Denver Broncos are an example of a team that likes the run zone blocking when running the ball.
Some running backs prefer one or the other and actually play better when a certain scheme is called. Again, that changes from person to person.
Overall there is no obvious better blocking pattern, which is why the usage is not overwhelmingly high on either side.