Who held the position of chairperson for the Communist Party of China before and after Zhao Ziyang?
SELECT ?value1 ?value2 WHERE { wd:Q17427 p:P488 ?s . ?s ps:P488 wd:Q99829 . ?s pq:P156 ?value1 . ?s pq:P155 ?value2 }
communist party of china: Q17427 zhao ziyang: Q99829