I did this to my Zafira before Christmas it is very easy. Remove clips, pull out bulb and replace.
However, if you want a manual to show you goto http://www.vauxhall.com/vx/static/content/pdf/ownersManuals/Cars/Zafira/ZafiraMay2003.pdf this is a copy of the Vauxhall Zafira user manual.
Good luck
Andy G
January 2007