"So they were unable to scale it," meaning to climb over it from above, "nor were they able to penetrate it," from underneath it.
﴿فَمَا اسطاعوا أَن يظهروه﴾ أَيْ: يَظْهَرُوا عَلَيْهِ مِنْ فَوْقِهِ ﴿وَمَا اسْتَطَاعُوا لَهُ نقبا﴾ من أَسْفَله
