Individual Track Zoom Reset for All Tracks ⌃⌥⇧⌘⌫
To be fair, this command is mentioned in the manual, but how to use Zoom effectively is no longer described in the documentation. The behavior of Zoom isn’t necessarily clear, and can appear to be almost magical in its behavior.
Another reminder to go read Chapter 4 of the Logic Pro 9 manual…
Individual Track Zoom Reset for All Tracks: Resets all zoomed tracks to the window zoom level.
While zooming, the top-left (and selected) event or region is kept in the visible area of the screen. In other words, the first selected region or event is retained in the zoomed window. If no selected region or event is visible, zooming is centered around the playhead. If the playhead isn’t visible, the current center of the window is retained.