There is no academic definition for “the zones”. Anyone might define his/her own.
However UA works with recovery zone, z1 to z4 and z5 (z5 is not really used I believe).
All is quite detailed in the books plus there is also a calculator on UA webpage.
Cannot believe they will change their zones.
Just check the last video.
Basically put AeT as upper limit of Z2, go 10% down and set this as upper limit of z1 one and another 10% down set this as lower z1 limit. For the upper limit of z3 take your AnT. But it is perfectly explained in the last group session.