They're both a Vz 58. The CZ 858 is just the civilian name the Czechs gave the rifle so it would be harder for the ignorant anti's to ban it. The CZ 858 is made on new, old stock, surplus parts. The finish is ugly but is very durable. I dragged my CZ 858, In which I always called a Vz 58 despite the CZ 858 name, thought the woods, carried on my back well deep woods trail riding dirt bikes, and the gun took a beating but it shot well, and the finish looked like it didn't even have a scratch on it. There are two known gremlins of the CZ 858. Mine had neither. I have since sold my CZ 858 but have purchased a CSA .223 Vz 58. The finish on the CSA is much nicer but not very durable. There has been lots of complaints such as the firing pin breaking, it not able to feed or extract properly, such and so. Again, mine has had none of those problems although, its only hit the 200 round mark as of yet. Its very accurate. 2.5" - 3" groups where as my 858 was 3" - 4" groups and this is at 100 meters not yards. My CZ 858 has had thousands of rounds though it trouble free only had the end of a shell get ripped off during extraction but I keep a well stocked tool box in my truck and some JB stick weld, the cleaning rod, and a quick tap on the JB stick weld popped the old case out. The CZ 858's groups were also consistent no mater what kind of ammo you gave it. The surplus stuff was closer to 4" well commercial Federal Power Shock SP was closer to 3".
I really miss my Vz 58 (CZ 858) but i'm also really enjoying my CSA .223 Vz 58. Preferably, Id like to have both of them but the CZ 858 is no longer being imported so all we have is the CSA Vz 58. My only complaint about that is the $900 price tag on the CSA vs the $650 price tag on the CZ 858. They both have 5 years of transferable warranty. If someone were to take my old CZ 858 and my current CSA Vz 58 and said, "your going to war, pick one" Id pick the CZ 858 just because I know it works as its had thousands of trouble free rounds though it. The CSA is new with only 200 rounds. With a lot of issue reports floating around and only 200 rounds though the gun, I'm still iffy if there will be any issues with it.