In the same breath

It can be used in the middle of the sentence, but your sentence feels odd to me. "in the same breath" is usually used when contradictory or disparate things are said or written one after the other. For example: "She said she loved me, then, in the same breath, said she was leaving." I wouldn't recommend using it to join arbitrary actions such as talking and walking down the street.

That's right that " at the same time " is similar as " in the same breath " I can notice that the original sentence is has superficial meaning which implies the previous action has happened in the same moment in which is the next action followed it. So logically , I think that we can't replace the first phrase with the second one ... when you asked why I will reply you that especially in this

Thanks, Mr. Wordy, I get it. Would it then be better to just write 'whilst also' in that case? Or, is there a better way?

I agree with Wordy that this is not typical. Although we no doubt consume breath while walking, the expression usually refers to utterances.

- Unless we mean quite literally at the same instant. "He kicked him in the shin while in the same breath shooting him through the heart." (Within the span of a single breath.)

This usage doesn't fit the sentence of the OP.

AnonymousThanks, Mr. Wordy, I get it. Would it then be better to just write 'whilst also' in that case? Or, is there a better way?

"whilst also" seems too laboured for such an everyday occurrence -- like there is something notable about talking while walking. You could say "He spoke to her as they walked down the street" (he was the one with something to say)