There aren't too many pitchers that don't run out of gas at some point.
On the walk, the ball was about an inch outside, and the call could have gone either way, or the batter could have swung. Same pitch could have had dramatically different outcome. But I'm sure you could see into Zimmnn's soul and could tell he was gassed, even with an out in that situation.
Have you watched JZ pitch this year? He's melted down in the 6th-7th quite frequently. It's not a coincidence, it's a pattern.