You can make it work. Though you’re mixing two ideas together. The concept behind the 4 week booster is to accumulate enough high intensity work over the week to pull your FTP up. Your long outdoor ride will wreck your legs and you’ll struggle to meet the necessary intensity on the 4 week programme. Could end up spiralling into a mess. Don’t underestimate those short workouts they do get tough in the last two weeks. Though, you can make it work, but you’ll likely just end up doing long weekend rides and a couple of interval workouts during the week and it’s not really that focused. Ultimately - better ways to spend your hours if FTP is your main goal.
The 4wk FTP booster is a bit of a hit or miss. I’ve done it and so have a few other people I know in real life, as well as the missus. I got a 5 watt boost on it. The worst I’ve ever gotten from 4 weeks of training on any FTP programme! Some guys scored worse on their 4 week test at the end of it. The missus had a 3 watt FTP boost. Again, her worst ever improvement for 4 weeks of FTP training. Really strange.
I think the 4 week programme needs a bit of work, including a better taper to the week 4 week FTP test itself. I’m thinking people who didn’t do well from it were fatigued when re-testting. I actually waited myself to get some freshness back before testing again. Still didn’t help me much. Anyway, if Zwift could pass on all the results to the coach who designed it and let him rework it a bit then that would be brilliant as I do love the idea of a high intensity 4 week FTP booster.
Not to put you off it though, I’ve seen a guy on here say he had massive results on it, though it was something like a 30% FTP boost. Think a lot of people didn’t really take him seriously, but still, I’m sure lots of people did have excellent results. The coach has a strong background, I wouldn’t dismiss his plan based on a small sample of people I know. Zwift has the data, rest of us only have anecdotes.
Personally, I have to unsub from Zwift for the winter. I was hoping they’d get some TrainerRoad-like ‘Sweet Spot Base’ programmes in by now, but time’s up, so back to TR for now. Zwift has nothing that can even remotely compete with that if you really are serious about boosting FTP.
Fingers crossed for next winter though!