Preferably, you'll want to allow for 3-5h of transit time in Johannesburg, so that you've sufficient time and energy to capture your connecting flight. Transiting in Johannesburg is quite straightforward; merely Stick to the indicators for ‘Intercontinental Transit’. The flight from Johannesburg to Harare requires about 1h 30m. *Fares exhibited https://www.theluxurybooking.co.uk/flights-to-zimbabwe-from-london/