I had the same experience when I was competing in eSports. I played a very fast paced and unique first person shooter that required complex and perfectly timed button sequences to dodge and attack at the same time. The game sent packets p2p so you had to predict where your opponent was about to be based on your ping to them, the shot was a hit based on where the character was when the packet was received. I played at the highest level and while I was normally not as good as my opponents, I would go into a zen state like what you described where time seemed to slow, I could predict my opponents movement easily and land shot after shot. I would either be the mvp of my team if I could get into the zone or be a non factor if I couldn’t. I never could figure out how that worked but I do feel like “flow” when coding is similar.