Gunplay,
If you are in California, you cannot buy the DSA Carbine in it's pictured state. I believe it has to have a fixed (welded in) mag.
If you have an AR already, and can add parts (I'm not sure on CA law), then the ZM may be your only Choice.
Aside from that, let's say you 1. Don't have an AR, or were going to get another one to use with the ZM kit, and 2. You have a dual residency in a free state so you can buy what you want.
My suggestions:
1. Factory DSA SA-58 Carbine $1300ish. Their DSA Stg-58A "kit" gun has a dealer cost (carbine) of $850. Get the kit gun, and save $400, they are excellent quality/fit/finish.
2. The ZM would run you $1700+ for a pre-ban lower to build it on and the ZM kit itself.
Buy the DSA (after Dealer Markup figure $1000), and get a post ban AR for $700 instead of just the ZM. Or, get a pre-ban lower and put it together yourself sometime.
The ZM is a nice concept (haven't handled one myself, so I can't say how they shoot). I prefer the FNC, and you can get one for close to the cost of a complete pre-ban lower with the ZM kit, and you can get a registered sear for them later if you want.
Alternately, you could get a pre-ban AK for just over $700 instead of the AR.
I agree with you on the Carbine being the best way to go. I like the handling of the carbine vs. the standard FAL rifle. The muzzle brake you picture is VERY loud, however (one reason to go with the kit gun and the non-functional muzzle device). I believe the gun you picure has the Stainless receiver, which adds significantly to the cost of the gun.
AFARR