[Zope] customize ZMI to hide objects?

How would I customize the ZMI to hide objects such as the Control Panel and DTML methods from certain user roles? We are building a website where users will change the content using the ZMI. We do not want the users seeing the Control Panel, DTML methods, or Python scripts since this would just confuse them. We just want the users to be able to see and edit the ZClasses that we have created for them. I have tried to look through the code, and I'm pretty sure I will have to modify some DTML code from the base Zope installation, but I'm not sure which files I will have to change. - Eric