condition 0%

That should not happen. There was a previous bug that would display "ghost" units with 0% combat effectiveness, but they could not move or engage in combat. I have never seen what you have described.

After a while the bomb with artilery and lost normally.

0% also represents 0.1 life points

As Nem stated, the unit still has a little life left to it. HP are broken into tenths, which you can find my clicking the unit on the map, then clicking the unit's image at the bottom of the screen to see it's full info card