NYASHA CHINGONO ZIMBABWEAN President Emmerson Mnangagwa vowed to do "what we can to remain in power", promising to revive an economy that has collapsed under his watch as he launched his bid for a second five-year term. Zimbabwe will hold presidential and parliamentary elections on August 23 which are expected to pit Mnangagwa, 80, of the ZANU-PF party against pastor and lawyer Nelson Chamisa, 45, of the Citizens Coalition for Change (CCC). The election comes amid a raging economic crisis, with high inflation and a currency that plunged more than 50% this month against the U.S. dollar. In remarks aimed mostly at…