HARARE – Zanu PF won all six National Assembly by-elections held on Saturday to secure a two thirds majority, with which it can now amend the constitution. Zanu PF candidates won in Pelandaba Tshabalala, Chegutu West, Goromonzi South, Zvimba East, Mkoba North and Seke – all seats which were won by the Citizens Coalition for Change in general elections last August. Sengezo Tshabangu…