Zooming

[SpeedLite]

Hi everybody.

This is my first ever post anywhere. I am a litle nervous but here goes.

I have seen some pics taken using the technique of adjusting the zoom during exposure. Is there a name for this? I am going to try it but wondered if anybody had any advice before I do.
Is it best to zoom in or out? What sort of exposure times should I use? How fast should I zoom? Should I turn off image stabiliser? Will the metering get confused so should I meter manually? Is there anything else I should take into consideration? Have I asked enough questions?
Any help welcome.

If anyone has any pics like this I would love to see them.