Complex sentence: After Jehoash was crowned, the covenant was renewed between God, the king, and the nation, and the Tyrian cult of Baal, which had started under Jehoram, and strengthened under Athaliah, was suppressed.
Split into simpler sentences: After Jehoash was crowned, the covenant was renewed between God, the king, and the nation. The Tyrian cult of Baal, which had started under Jehoram, and strengthened under Athaliah, was suppressed.