You certainly can. There are just a couple of things I would suggest if you decide to do this.
First, I would make allowance for differences in training conditions. Suppose that you do your initial zone test on a cool spring day. If summer temperatures are significantly hotter, I would suggest either adjusting your target paces or redoing your test in the hotter weather.
Second, I would also pay close attention to perceived effort. Pace and power are good indicators of workout intensity most of the time. But there are those days when you’re feeling more run down, dehydrated, etc. On these days, my suggestion would be to slow down to what feels like the appropriate effort. Otherwise you risk pushing harder than you should. I’m speaking from experience as I’ve powered through and pushed too hard a few times.
The experts here might have something else to say, but hopefully this helps.
Alan, thanks! And, Shelly, from a technical point of view you can switch intensity types within in the same distance for free by making a Level Guarantee request at https://www.8020endurance.com/contact/