Zip's shares surged 20% after announcing a $30 million buyback plan.The buyback plan aims to increase shareholder value and stabilize the stock amidst market volatility.Zip's shares reached a high of A$1.430, making it one of the biggest gainers on the S&P/ASX 200 index.The buyback program, set at A$50 million, is expected to alleviate market pressure.