Mthembu holds the key to an ambush and a quick end of Zuma.  Yes, threaten dissenting MP's with disciplinary action and expulsion if they vote against Zuma in the no confidence debate, but in the background organise to vote for the motion.  And get Ramaphosa and Mantashe to address the ANC caucus just before the vote (Zuma will also address them ). Turn the no confidence debate into a me or him vote.  All the opposition members plus 20 (SACP) MP's and you only need 30 ANC MP's.  But I bet that once those MP's see which side of the bread is buttered and what that holds for them only the most deeply enmeshed in state capture will support Zuma.  

QED