Arda Wiraz's Night Journey

It's very common that atheists rebuke the claim that the Prophet flew on a "winged horse/donkey" (i.e., "al-Buraq") to the seven heavens, in the story of al-Isrā' wal-Mi'rāj, and they claim as well that this story was plagiarized from Zoroastrian mythology, specifically the story of Arda Wiraz. In reality, there is no description of a "winged horse/donkey" anywhere in the entirety of Hadith literature. The creature Prophet Muhammad was riding (i.e., al-Buraq) wasn't winged, and was neither the size of a donkey nor a mule, but something in between:

Al-Buraq; a white animal, smaller than a mule and bigger than a donkey was brought to me and I set out with Gabriel.

Bukhari 3207

Then a white animal which was smaller than a mule and bigger than a donkey was brought to me, the animal's step was so wide that it reached the farthest point within the reach of the animal's sight. I was carried on it, and Gabriel set out with me till we reached the nearest heaven.

Bukhari 3887

I was brought al-Buraq, who is an animal white and long, larger than a donkey but smaller than a mule, who would place his hoof a distance equal to the range of version.

Muslim 162a

I was then brought a white beast which is called al-Buraq, bigger than a donkey and smaller than a mule. Its stride was as long as the eye could reach. I was mounted on it, and then we went forth till we reached the lowest heaven.

Muslim 164a

Furthermore, it was used only for the traveling between Mecca and Jerusalem; al-Buraq was tethered when the Prophet (ﷺ) reached Jerusalem, and the ascension was with Archangel Gabriel:

I mounted it and came to the Temple (Bait Maqdis in Jerusalem), then tethered it to the ring used by the prophets.

Muslim 162a

Even if al-Buraq was a "flying donkey," there's nothing fundamentally unrealistic about "flying donkeys" for that matter. For atheists, those who don't believe in miracles, it's just an arbitrary consequence of nature that donkeys don't fly.

Now that we've explained that al-Buraq didn't fly for that matter, we're now back to the issue of plagiarism. The claim that Islam borrowed the "flying beast" concept from the Book of Arda Wiraz is false, and it's actually the other way around; Zoroastrianism was influenced by Islam on this issue. According to Encyclopedia Iranica, this story in its definitive form was traced back way until the 9th-10th century after a series of redactions (which are lost to time), concluding that the final redaction of the text probably refers to the early Islamic period. It becomes clear therefore that the Zoroastrian book, Arda Wiraz, was actually the one that plagiarized the story from Islam.