catfood
AGAIN
There's another RTS-FPS hybrid that came out around the same period (autumn 1998) called Urban Assault, which you can download from here along with some other mods. It's more on the RTS side, than FPS side, since you actually have a map and a unit squadron where you can form new squads and give them various AI settings. It also features a non-linear campaign with a C&C style map that offers you a couple of new missions each time you complete one, although eventually you're going to want to do all of them since they contain research that you want to obtain. The original game has only one side that you can play as in singleplayer, however there are 2 unofficial add-ons that allow you to play as another 2.
The game is not as good as BZ, though, but it's still worth a try. Its main downside is that there's really no mission variety, save for the terrain and factions you face on a map, unlike BZ where you're always given a different objective. In UA it's always kill all the enemy bases. Still, the game is addictive and VERY challenging, so I'd say it's worth a try especially since it's free.
The game is not as good as BZ, though, but it's still worth a try. Its main downside is that there's really no mission variety, save for the terrain and factions you face on a map, unlike BZ where you're always given a different objective. In UA it's always kill all the enemy bases. Still, the game is addictive and VERY challenging, so I'd say it's worth a try especially since it's free.