Heartrate Percentage Correlation to Zones

I am 16 weeks into the Ultra Plan and feel I have chosen the right plan to prepare me for CDA.  I have sticking with the heartrate percentages as specified, but in the past have used heartrate zones (1,2,3,4,5a,5b,5c) based on a field lactate threshhold test.

I was wondering what percentages based on max heartrate should correlate with what zones, such as 75% of 220-age should fall into zone 1 or should it fall into zone 2?

Thanks for the excellent training plan and incredible information on this website.