I recommend that you read about flow then.
The original idea of flow(in the zone) comes from this book and author, but is obsolete now:
https://www.amazon.com/Flow-Psychology-Experience-Perennial-...
I recommend this book and audiobook about gammification to understand flow better.
https://www.amazon.com/Reality-Broken-Games-Better-Change/dp...
Whatever breaks the game in your work, stops the flow. For example, instant feedback is very hard to get creating software unless you design for it(like using REPLs and reusing almost everything).
Other things that the book mentions break your game too(not having clear rules, being alone)...
Another important thing is thinking too much rationally. The logical mind is so slow getting results that you break the instant feedback.
Also working too much in low level has way slower feedback than working with higher level languages. I metaprogram lower level languages for this reason, I am orders of magnitude faster.
>The zone isn't about stress per se.
Sorry, I was not eloquent enough. when I talk about stress I am referring to stress in general: Mental, emotional, or physical stress.
That is, if you are doing something difficult mentally, you stress your brain.
For every stress you need time to recover.
You can do 10 hours without recovering if the stress is low. If the stress is high, you will only be able to do 4 hours.
It is very easy to understand, you can walk for 8 hours, but you can not run for 10 hours. A marathon is about 4 hours or less.
What I am telling you is that if you run for 4 hours hard mentally and do not recover, you will not be able to work another 4 hours of hard work, unless you rest.
Nothing will do, no technique will do unless you rest.
Of course you need to do right lots of other things too. But don't say it is impossible just because you can not do it.