There were all kinds of grand plans for TA mods previously; installers, autoupdates, mod switching launcher, improvements to the engine, uncounted new features for modders to use and so on. Some of all that has actually happened, some is being worked on, but overall the TA modding community has been in disarray ever since N72 disappeared and took the community patch project with him.
TA Zero was hurt the most because until then N72 had been making all the buildpics, doing a lot of technical work, building and upholding this website, and written newsposts and various text files.
Although slowly and randomly, TA Zero has still been progressing in relative silence over the last years. Alpha 4b patch release has been essentially ready for a while now, new test builds being available on the forum every here and then. There's also a handy thread that summarizes all the new stuff you should get. The changelog has hundreds of lines, including many new units, some bug fixes and a crazy amount of balance adjustments, so everyone still playing Zero should go and grab the latest Alpha 4b test build files; just unzip into your TA Zero folder and replace old Alpha 4 files.