Oh, That's Hard!

S 79:27 Are you a harder creation or is the sky that he built?

Ibn Kathir:

Creating the Heavens and the Earth is more difficult than repeating Creation in refutation of the claim rejecting resurrection due to the renewal of creation after its original state, Allah says;ءَأَنتُمْ(Are you) `O people'أَشَدُّ خَلْقاً أَمِ السَّمَآءُ(more difficult to create or is the heaven...) meaning, `rather the heaven is more difficult to create than you.' As Allah said;لَخَلْقُ السَّمَـوَتِ وَالاٌّرْضِ أَكْـبَرُ مِنْ خَلْقِ النَّاسِ(the creation of the heavens and the earth is greater than the creation of mankind;) (40:57) Ibn Al Kathir commentary for verses 79.27-33

Further reading: It Gets Easier With Practice