Complex sentence: She intervened decisively in international agreements as important as Treaty of Almizra with Castile (1244), signed with the condition that Zayyan ibn Mardanish surrender of the city of Valencia, which she triumphantly entered with her husband on 9 October 1238.
Split into simpler sentences: She intervened decisively in international agreements as important as the Treaty of Almizra with Castile (1244). It was signed with the condition that Zayyan ibn Mardanish surrender of the city of Valencia, into which she triumphantly entered with her husband on 9 October 1238.