baishan

I appreciate you telling me how to complete map 4, but I'm not going to play this map again.

OK I managed to destroy the centre one you can see from the starting point, and the one on the left side.  The hints on the wall where you start show the HP of each object.  For the centre/silver one, you can just stay where you are and shoot it from a distance with the sniper rifle while killing any Tanks that spawn/drop from above.  Then you can use the supplies before dropping down to the floor to destroy the rest.  The one on the left is easy because there's ammo close by on the above walkways, but I dunno how to deal with the one furthest back where there are logs & buses.  I don't see any supplies nearby, and you need a lot of ammo for each.

Map 4 seems to be a boss fight.  I think you need to destroy the diamond-shaped things, and the floor thing is caused by burning chunks of rock that are regularly rising in the background and crashing down, making the floor lava for 3-5 secs.  Just have to run up the ramps or climb the ladders before that happens.  Tanks are regularly spawning in random places and chasing you down, so you can't take your time and you have to mind your ammo consumption as I haven't seen any ammo piles on the high ground.  I don't know how much damage needs to be done to the targets.