Ravi please read through the posts at the begining of this topic there is a lot of information for you there or contact RSN for extra help.
The only other thing to do if you are missing original game files is to first make a backup of your saved games folder,zoo.ini file and any downloads you have somewhere on your system (Not the ZT Directory) uninstall your game ...use the registry cleaner located
Here to be sure all traces of ZT are gone from the registry. reboot your system and then reinstall the game. Start the game to be sure missing files are now there.
Before you install any other downloads install wildwings by putting the ztd files in the updates folder the dll files in the main ZT folder and don't install the maps. Start he game and see if it is working for you.
When it is working then 1 by 1 reinstall the downloads checking to be sure there are no conflicts to crash the game.
Following these directions it should work for you. If it does not then please contact RSN for technical support for his creations as there is nothing else we can do to help you.
Yellowrose