Complex sentence: After the Rabin assassination, he helped found Tzohar, whose aim was to lessen the tensions between religious and non religious communities that had been exacerbated by the fact that the assassination had been committed by a young Yeshiva student.
Split into simpler sentences: After the Rabin assassination, he helped found Tzohar, whose aim was to lessen the tensions between religious and non religious communities. Those tensions had been exacerbated by the fact that the assassination had been committed by a young Yeshiva student.