zoom in and pan trough video during playback?

I is it possible to zoom in and pan trough video files during playback on iphone 3GS?
Yes.

I know that there is a zoom inside accessibility inside settings but is it possible to use that during video playback?

Yes. Three-fingered double-click to turn it on or off. Three-fingered drag to move the zoomed image.

Sometimes during playback I need to enlarge some parts of video in a way to read numeric settings or something similar.

The video will have been compressed for use on the iPhone, so zoom may help, but it won't be able to show detail that was lost in the compression.