Please read the article. Author intentionally simplified the zone scheme to three zones instead of five, seven, etc. I also explained it above, Z1 – everything under AeT, Z2 – everything between AeT and AnT, Z3 – everything above AnT.
His conclusion about this type of training is: “It has been shown that switching between low-intensity and high-intensity training is better tolerated, less monotonous and protects against overuse.”