Ideally, you need to allow 3-5h of transit time in Johannesburg, so that you have enough time and energy to capture your connecting flight. Transiting in Johannesburg is very uncomplicated; simply just Adhere to the symptoms for ‘International Transit’. The flight from Johannesburg to Harare can take about 1h 30m. https://www.theluxurybooking.co.uk/flights-to-zimbabwe-from-london/