There is a punishment of lashes in Surah e Noor for adultery....there are punishments of rajm to married couple (in Hadith books)
Read what you wrote, does it make sense to you? The Quran is saying lashes and books scribed by men are saying gruesome torture till death!
There is no separate word for adultery or fornication is Arabic, its the same word, zina. And once again use your god gifted common sense, when Allah s.w.t can go into such detail about it, you think if it really was the case he would not mention the difference between the two. Specially since the latter one has such a horrific outcome!
It makes no sense that he would in detail mention one crime and its punishment and then totally skip the same crime just done in slightly different circumstances which has a earth shattering outcome.
This is what happens when you start using questionable hadith as your primary book of religion rather than Quran and start listening to such sectarian old horn dog mullahs.
Imam Malik born, lived and died in Mecca. And was the first person to scribe a compilation of hadith within a century of the Prophets passing. He himself said don't take your religion from the hadith.
Hadith are books of Islamic history and biographical in nature, not books of religion, jurisprudence or edicts. If you do then you should support groups like Daaesh, Qaeda, TTP and Taliban. Because they are the ones who follow the hadith the best.