You'll need to add the following to the indicated plist
And download the attached zip'd tiff file for a proper icon (put it in the same directory as the plist you're modifying)
I found the original for this at
http://www.howardforums.com/showthread.php?t=1255159
and tweaked it a little for the Z6c.
<!--
insert this in the /Applications/iSync.app/Contents/PlugIns/ApplePhoneConduit.syncdevice/Contents/PlugIns/PhoneModelsSync.phoneplugin/Contents/Resources/MetaClasses.plist
file (under the top-level <dict> element)
-->
<key>com.motorola.rizrZ6c</key>
<dict>
<key>Identification</key>
<dict>
<key>com.apple.gmi+gmm</key>
<string>Motorola CE, Copyright 2000+Motorola CDMA Z6c Phone</string>
</dict>
<key>InheritsFrom</key>
<array>
<string>com.motorola.usb-bt.0x22B8/0x4902</string>
</array>
<key>Services</key>
<array>
<dict>
<key>ServiceName</key>
<string>com.apple.model</string>
<key>ServiceProperties</key>
<dict>
<key>ModelName</key>
<string>RAZR Z6c</string>
<key>PhoneIcon</key>
<string>MOTZ6C.tiff</string>
</dict>
</dict>
</array>
</dict>