Routing a client's US-origin cargo to Zimbabwe through Durban instead of via Europe: which US port, and what happens after Durban?

We sold a machine into Zimbabwe on delivered terms. The forwarder suggested Beira; I chose Durban because the buyer knew it, and am told Cape Town makes the second leg cheaper. The cost was the bonded road leg from Durban and the wait at Beitbridge. Two ways to run that leg, learned when the truck stopped: the line's haulage, box their problem, clearance on their schedule; or a bonded trucker, clearance yours to push, and so is the box. Which would your client rather hold at Beitbridge?

Seen from Denmark, as vocabulary rather than advice. A forwarder I use for African deliveries routes his Zimbabwe cargo through Walvis Bay, and says the onward leg is why. The port-to-border road leg is, in Union terms, external transit: duty suspended under a guarantee across South Africa and discharged on the Zimbabwean side. Both regimes treat the sailing as the easy part; where they may part company is who holds the guarantee and who is chased when a movement is not discharged, a question for whoever is on the ground.