If possible, you must allow three-5h of transit time in Johannesburg, so that you've enough time for you to capture your connecting flight. Transiting in Johannesburg is quite easy; basically Adhere to the indications for ‘Intercontinental Transit’. The flight from Johannesburg to Harare normally takes about 1h 30m. By clicking https://www.theluxurybooking.co.uk/flights-to-zimbabwe-from-london/