Banks’ credit losses are starting to spook the stock market. - AFP/Getty Image Struggling to find their way amid an ongoing economic-data blackout and renewed trade-war tensions between the U.S. and China, investors already had enough to worry about this week. Then a regional lender piled on one more thing: Another large credit loss, possibly stemming from fraudulent activity. In a regulatory filing published Wednesday evening, Salt Lake City-based Zions Bancorp ZION revealed that it would include a loan ...