The ghost of Compagnie des Machines Bull SA’s Zenith Data Systems misadventure came back to haunt it and cast a pall over its first half figures. Bull, which dumped Zenith off into Packard Bell Electronics Inc in return for a 19.9% stake in the enlarged company earlier this year, made a consolidated net loss equivalent to $122m, up from a $25m loss last time, and revenue was down 3.6% at $2,280m. The company said its personal computer activities made a loss of $132m while its other activitie s had made a profit of $9.8m. For the full year, the company says it is aiming for a 1996 profit of more than the $153m it made in 1995. After a first half marked by the merger of Zenith Data Systems with Packard Bell, the group remains confident o n the year 1996, Bull said.