Zillow Offers is the company’s “iBuyer” service that aims to digitize the homebuying experience from start to finish. (Zillow Photo) Zillow Group says it is making good progress unloading homes it owns, announcing today that it has sold or is under contract to sell more than 50{3e92bdb61ecc35f2999ee2a63f1e687c788772421b16b0136989bbb6b4e89b73} of the homes that it planned to sell as part of its decision to shut down its Zillow Offers business unit. The Seattle-based real estate company also announced that the board authorized the purchase of up to $750 million worth of Zillow stock.  Shares of Zillow — which have been hammered in the past six months, dropping 51{3e92bdb61ecc35f2999ee2a63f1e687c788772421b16b0136989bbb6b4e89b73} — rose in after-hours trading.…