Complex sentence: On 15 April 2009, Ilunga turned his loan move into a permanent four-year contract with West Ham which took immediate effect straight away when the 2009 summer transfer window opened.
Split into simpler sentences: On 15 April 2009, Ilunga agreed to turn his loan move into a permanent four-year contract with West Ham. The deal completed, Ilunga joined on permanent terms when the 2009 summer transfer window opened.