In a nutshell: If you own Generals, get ZH!
Everything is better and easier for modding. Plus in ZH, EA actually included all the models they haven't used, which is really great if you wanna make a mod that brings all that stuff back in, or just get some cool new models.
And even if you don't mod (what the heck are you doing here
), it improves game experience substantially. Especially multiplayer: with the seperate Generals it's a blast!