Danylo, thank you for the stupidest translation ever made!

Uly, I have no idea to what language Danylo translated your sentence, but there are something wrong with the Russian. Where did you get it from?
(to be continued...)

1. «Я ВНЕЗАПНО услышал.» Внезапно можно совершить какое-то действие - атаковать, выскочить из укрытия, затормозить и т.п., но не услышать или увидеть.
2. «Застегнув молнию рюкзака, я УСЛЫШАЛ…» Тоже странно звучит. Застегнув молнию рюкзака, я вышел на улицу - sequence of actins. Застегнув молнию рюкзака, я почувствовал, что в рюкзаке что-то шевелится / услышал, что в рюкзаке что-то пищит - result of action. In the context, he heard something not connected with zipping the backpack up.
I can’t prove or explain all that grammatically, but it sounds like written by a child or someone whose Russian isn’t good enough to write literally.
I would suggest my revision:
«Я застегнул молнию рюкзака и вдруг услышал, как…»

My English version:
Just as I zipped up my backpack, I suddenly heard a passing car come to a halt sharply.

This is the second time I see that this text isn’t worth studying. This person just doesn’t know how to write Russian. Thank you for the translation and the in-depth explanation!

🤩

I wouldn't say the Russian version is terrible. It may not be the best, but it's fully acceptable. I don't see anything wrong with "внезапно я услышал". Yes, it's less common than "вдруг я услышал" but it means the same thing and was being used in books.
I don't know who the author is but every writer has their own style and I think that's great. (unless it sounds really wry)

This is just a guy who wrote his memoirs of a bike trip across Kazakhstan. I’ve been helping him by checking his translations and I wasn’t sure about the first part of this sentence. Now I know)))

So, if this is just a guy then we don't expect him to be a top notch writer. There might be more common and less common phrases in the text and that's fine.

Ok, that’s actually a good assessment. Thank you.

I think there's nothing wrong with Russian.

👍🏼

застегнув – деепричастие. We rarely use them in a spoken speech. That widely uses in a written.

Я согласна с Александром, что «Я застегнул молнию рюкзака и вдруг услышал, как…» звучало бы лучше.

Thank you! I’ll change it in my notebook.