The preview can quickly display images, PDF, HTML, and text based files.
To open the preview choose View > Preview, click the preview button in the window's bottom-right corner or press ⌘⌥P on your keyboard.
As long as the preview is opened, it will display the currently selected file. Only one file can be previewed at a time.
If the file type is not recognized automatically, BetterZip will show the file's icon and a Preview as Text button. Click this button to force BetterZip to display it as text. Be careful not to use this with huge files like movies, because this can lock up BetterZip for some time.
To preview files in an archive with Quick Look select the file and press the spacebar. You can move the selection with the arrow keys without closing the Quick Look panel. Press the spacebar again to close the Quick Look panel.