The Z2 is the newest version of the original 6Z. The 6Z was designed for use with a firearm. There are multiple rubber rings to adjust to your grip-size. With the "C" versions adding to increased finish protection (HA), weight, pocket clip, and shock-isolated head (M2). Also, there is only one rubber ring, which is fixed, to allow for no grip-size adjustment on the C2/M2.
I personally carry a 6Z in my mag pouch. I also have the X200B on my pistol. This combination has worked well for me. The combo mag pouch solves carry issues if you are carrying a firearm. If this doesn't work for you, consider the E2e. This allows for a pocket clip, lightweight, small diameter, easy carry. (Maybe the L4/L2 if you go LED.)
Personally, for "standard carry", the C2/M2 are too bulky for me. However, if I were to carry with a tac-vest, call-out bag, or other load-bearing gear, the C2/M2 or, an M3, would be easier utlized.
If there is any down-side to the Z2 is the Incan. bulb is not isolated like the M2. However, the smaller head, and those features mentioned above, outway that issue to me. Plus, you should carry more than one light anyway. If this was a mnajor issue to you, consider a good quality drop-in LED. Just know that the "throw" will be less, and is also less contrasty. This could diminsh your longer distance I.D. capabilities...
I hope that this gives you more insight on your options. Thankfully this is a great Forum, with huge amounts of "Bright" Members that know many angles of this arena of lights. This is just my brief input to help out.
Be Safe!
Don