I'm older and I find myself getting into the zone much easier now than in years past. Personal life distractions can hinder you and clutter your mind.
What I'm about to say though, is what I attribute most of my success in being able to falling into the zone with conscious control.
I feel that the more often you experience that state, the easier it is to achieve it. I very strongly feel that 9 ball is the absolute worst game to play when attempting to become experienced with getting into dead stroke. In 9 ball you shoot, you stop, you rack, you stop, you shoot, you duck, your innings are short.
None of that is too much of a problem if you have already played enough to have experienced dead stroke often. But if it is still one of those things that is fleeting, I am convinced that to get familiar with the feeling, NOTHING does it like straight pool. Once you experience it often enough and long enough in straight pool, it becomes easier to carry over to other games.
Shoot, I can find dead stroke pretty readily now even playing One Pocket.
Now .... lol my "in the zone" isn't running hundreds,

but it is 30s and 40s with an occasional higher blip.
I think as mentioned in an earlier post, killer instinct has a lot to do with staying in the zone also. I never really had a ton of that, I just enjoy playing.
I think practicing getting into the zone in and of itself is important and 14.1 is the ticket to finding it.