Whittaker Corp., Los Angeles, reported that it has acquired Zeta Laboratories from Computer & Communications Technology for $39 million . . . Inland Steel Co. said it plans to form a holding company to control existing operations and strengthen its ability to make acquisitions and enter joint ventures . . . AMR Corp. said its American Airlines unit had a pretax loss in its first quarter . . . Mexico announced that it has arranged a $400-million loan from the World Bank but must hold further talks with international bankers and officials to win the full $6-billion rescue package needed this year to combat its financial problems . . . Security Pacific Corp., Los Angeles, reported that it has acquired Professional Corporate Service Group, a foreign sales corporation management company, for undisclosed terms.