The Zoom is stored in the Document Properties, so if you import document properties across all files in book you should be set.
Personally, I'd recommend either importing a MIF fragment for the zoom, or looking at Rick's ImportFormatsSpecial, which breaks up the things you can import from a given doc's document properties.
*This is from memory, so let me know if you find otherwise.
Thank you very much for the reminder. I have Rick's Import Formats Special script, and yes, it also has an option to import only the View settings. I use this script almost daily, but I had overlooked this option.