This explanation is pretty messed up and confusing...and flat out wrong in many ways.
A 3-4 is a Front. A Zone Blitz is a type of blitz. A team doesn't run a 3-4 Zone Blitz as a type of defense. It may be a philosophy, a way to get pressure, but not a base.
The basic concept behind the Zone blitz is to drop a player, like a DL who would not normally play coverage and send an LB on a stunt. If the QB reads blitz, he may just drop it off into the flat on a "hot read" and throw it right to a DE that dropped. Generally, the QB is taught to "throw into the hole" created by the blitzing LB. Before the Zone Blitz concept, he would not expect to see a 3-4 DE or NT in coverage.
The base coverage played behind the 3-4 is generally a 2 Deep Zone. Your description of a 3 Deep with the SS in Deep Third coverage is not ideal.
