Honestly i still haven't played the games but its on my wish list
ZOE 1 isn't too bad. ZOE 2 is just pure awesome and it still holds up quite well even today.
Picture piloting a Gundam from the Gundam Wing universe. That's how the game feels. You are piloting one very powerful mech (that flies and hovers), but your enemy has a few ace pilots and a lot of computerize units (like the Mobile Dolls).
My personal favorite part is playing the first stage, where you are on a winter planet. Ice glaciers everywhere, it's snowing hard and all of a sudden a swarm of 50 unmanned mechs come after you. The amount of power your mech has can easily kill them (beam cannons, light sword, vulcans, etc..). Plus you can grab a mech and throw them into the glaciers (very pretty looking).