(… وَكَذَٰلِكَ نُصَرِّفُ الْآيَاتِ ) (And thus do We diversify the verses …): Meaning, we flip the signs, explain them and make them clear. This verse refers to all the universal signs and the Quranic verses which exist and are dispersed throughout this universe.  

  (… وَلِيَقُولُوا دَرَسْتَ… ) (…so the disbelievers will say, “You have studied,”…): They also said:

 وَلَقَدْ نَعْلَمُ أَنَّهُمْ يَقُولُونَ إِنَّمَا يُعَلِّمُهُ بَشَرٌ لِّسَانُ الَّذِي يُلْحِدُونَ إِلَيْهِ أَعْجَمِيٌّ وَهَذَا لِسَانٌ عَرَبِيٌّ مُّبِينٌ

(And We surely know that they say, “No one is teaching him except a human.” But the man they refer to speaks a foreign tongue, whereas this (Quran) is (in) eloquent Arabic) (An-Nahl: 103)

So, they accused the Prophet (saws) of learning the Quran, not from His Lord (swt), but from someone else.

(  وَلِنُبَيِّنَهُ لِقَوْمٍ يَعْلَمُونَ… ) (…and so We may make the Qur’an clear for a people who know): The Prophet (saws) is tasked to legislate the Islamic rules, and to explain all that has been revealed, as Allah (swt) says:

وَأَنزَلْنَا إِلَيْكَ الذِّكْرَ لِتُبَيِّنَ لِلنَّاسِ مَا نُزِّلَ إِلَيْهِمْ وَلَعَلَّهُمْ يَتَفَكَّرُونَ

(And We have sent down to you (O Prophet) the Reminder, so that you may explain to people what has been revealed for them, and perhaps they will reflect) (An-Nahl: 44)

Therefore, any explanation from other than the Prophet (saws) cannot be accepted and should be thrown down the rubbish chute.