something that has always bothered me about the zombie apocalypse mod is the fact that the inside of cities is always a constant war, and it really brings down the stability of the game. I was wondering if it were possible to delete the changes to these cells so that no zombies spawn in these areas. I know a similar thing can be accomplished in morrowind with the enchanted editor, and in oblivion(forget what tool). How would i go about doing this?

The editing tool for Fallout 3 is called the G.E.C.K. (yes, it's kind of a joke). It is available http://fallout.gamesas.com/eng/downloads/geck.html. You will need both the main download and the 1.5 update.

If you need help in figuring out how to do what you want in the G.E.C.K., the Wiki can be found http://geck.gamesas.com/index.php/Main_Page. There are also a number of http://www.gamesas.com/index.php?/topic/952768-geck-video-tutorials-on-you-tube/ showing how to do various specific things using the G.E.C.K..

If you run into trouble, the http://www.gamesas.com/index.php?/forum/46-the-geck/ are available to get help.

Happy modding, and good luck!

can't tessnip delete cell data from mods?

Yes, however you won't get much of an overview on how the mod is put together and how the data you're deleting relates to other data in the mod from Tessnip. You'd have a better chance of avoiding possible catastrophic destruction of the mod by using http://fallout3nexus.com/downloads/file.php?id=637, but many users find it confusing to understand at first, especially if they're not familiar with mod construction. However, there is http://fallout3nexus.com/downloads/file.php?id=8629 that might assist in that.

I assumed, possibly wrongly, that you were after the official. Bethesda-created tools to edit mods, links to which I provided. The G.E.C.K. is by no means perfect, but has the benefit of being officially sanctioned, fairly well-documented as to its operation, and comprehensive in the sense that it often gives you immediate notification if you, say, delete an object that's used in a script elsewhere in the ESP, for example. In an edit such as the one you're proposing, that might turn out to be critical information.