Volatility with international trade didn't serve Zim well in its second quarter.The stock of logistics specialist Zim Integrated Shipping Services (ZIM -1.42%) landed in negative territory on Wednesday. Investors reacted unhappily to the company's second-quarter earnings release published that morning. With its resulting 1.4% slump, Zim had a worse finish to the day than the S&P 500 index (which was down only 0.2%).Second-quarter slumpsDuring the quarter, Zim's revenue fell by 15% year over year to almost $ ...