"The yellow ducks are not jumping out through the window, but flying out."

Translation: A sárga kacsák nem kiugranak az ablakon, hanem kirepülnek.

[GerSzej]

A sárga kacsák nem az ablakon kiugranak, hanem kirepülnek was rejected.
1. why is this word order rejected?
2. why kiugranak and not ugranak ki, since nem is in front?

[vvsey]

Remember, "nem" negates whatever comes after it. And, in this comparative sentence, the basic structure is "Not A but B". So, what are you negating in the first part of your sentence? The window! "Nem az ablakon... ". Contrasted with "kirepülnek". So, you are saying:

"Not (through) the window ..., BUT they fly out.".

Compare this with the sentence above. "Nem kiugranak...., hanem kirepülnek."
"Not jumping out ...., BUT flying out.".

And, 2., maybe it is obvious by now that the verbs are in focus. After all, the first verb is negated and a second verb is offered instead. The verbs play the most important part. They are in focus. And what happens when a verb is in focus? That's right, it stays intact! :)

Makes sense, right? :)

[GerSzej]

Yes, it makes perfect sense in a Hungarian logical way. Always clear explanations though, thank you.

[vvsey]

Always happy to help, you are welcome!