Cycling Fitness / Training Advice

In either case I'm pretty sure it's %V02 max rather than FTP. Although granted it's less likely you'll know what your power at V02max is.

Found this from a US coach at Evoq:

The boundary between zone 1 and 2 is: 0.77 multiplied by your 60 minute max average watts.

The boundary between zone 2 and 3: your 60 minute average max.

The upper end of zone 3 is your 6min power.

As an example mine would be

Z1: 0-267w
Z2: 267w - 345w
Z3: 345w - 423w