I agree with Tankshack,
From the pix I've seen

PzKpfw IV's with turret skirting, only had the front plate and gun mantlet coated in zimmerit.
The turret skirt itself was seldomley coated with zimmerit, although I have a pic with the side plates on a PzKpfw IV coated with zimmerit.
Study as many pix as you can.
Do you have much reference material???
go to :
http://babel.altavista.com/tr and enter the following web site :
http://www.achtungpanzer.bos.ru/index.htmlThis is a great site for pictures.
All the best