I had the same problem with unzipping 2.5, used both WinRar and 7Z rip. Both times, the files wouldnt extract properly. So . . . I created a new folder in the BTS mod folder naming it ROM 2.5.
Dragged and dropped all the files, and ROM works . . .
However, gameplay is very sluggish (moving units, entering the city screen etc.) and for some reason when I have multiple units stacked, only one unit shows. I cannot select individual units by picture. I can only select by right clicking. However, when getting to upper levels this will be a problem, when trying to assemble specific forces
What did I do wrong? I am a modding novice . . .