There is an instruction for meditation regarding the breath which goes, Let a long breath be long and a short breath be short. But can I find where that is mentioned in the edition of the Eihei Koroku I have! Anyway the gist is that Zen Master Dogen recommends that breathing during formal meditation be allowed to be natural and to not interfere in any way with breath, including counting. He is actually rather strong on the subject of counting the breath during meditation. He simply does not hold with applying methods and practices to help calm the mind. And rather scathing of those schools that do! We very occasionally give instruction on counting the breath with the warning that like any tool it will need to be put down eventually. Sooner rather than later.
Allowing the breath to be natural one sometimes feels that breathing has stopped all together! But it is important to breathe and not hold it which is a habit some people have developed. At other times the breathing seems rough, noticing is all that is needed. Noticing is letting it go, if that is your basic intention.
In daily life situations though, say when emotions such as anger or frustration are in the ascendency, it is helpful to deliberately slow down the breathing which inevitably becomes elevated with such emotions.