Unfortunately I don't have much more information about the game (just some memories about how it looked).
You could capture factories and produce units.
For unit production, you could create custom units (basicall something like: "Wheelbase" and "Gun").
If I remember correctly, this was important because there were also Biomes (e.g. snow), which you needed to consider.
I think the grid where the units moved, were also just squares (even though the camera was from an isometric perspective).
In my memory it always feels like a predecessor to Akte Europa.
Also it is not KKND or Earth 2150.
Does anyone have an idea?
//edit: A kind of similar looking game is "Nether Earth" even though it's no the one I am looking for - but maybe it helps.
//edit2: Thanks u/AstralMecha -> https://www.myabandonware.com/game/colony-wars-2492-jbm it is!