[nicbou]

As commented a minute ago, I spent a year aggressively muting distractions (then kept doing it when they pop up): https://nicolasbouliane.com/blog/silence

This helped a lot, although a lot is left to discipline.

Another aspect is creating the right conditions for focused work. That means a quiet environment, a well-rested and fed body, and possibly an advance planning of meals and other necessary distractions.

If you want to stay in the zone, make the zone a comfortable place.