DoCmd.OpenReport "Отчет1", acPreview Reports("Отчет1").ZoomControl = 100 ' 0 - 2000
Еще варианты
DoCmd.RunCommand acCmdZoom10 DoCmd.RunCommand acCmdZoom100 DoCmd.RunCommand acCmdZoom1000 DoCmd.RunCommand acCmdZoom150 DoCmd.RunCommand acCmdZoom200 DoCmd.RunCommand acCmdZoom25 DoCmd.RunCommand acCmdZoom50 DoCmd.RunCommand acCmdZoom500 DoCmd.RunCommand acCmdZoom75 DoCmd.RunCommand acCmdFitToWindow