Complex sentence: Al-Qaeda/Al-Nusra has been trying to take advantage of ISIL's rise by trying to present itself as "moderate" compared to ISIL while it has the same aim of establishing sharia and a caliphate but doing it in a more gradual manner.
Split into simpler sentences: Al-Qaeda/Al-Nusra has been trying to take advantage of ISIL's rise by presenting itself as "moderate" compared to ISIL. While it has the same aim of establishing sharia and a caliphate, it intends to implement it in a more gradual manner.