howl--I'm trying to follow your qs. Started w/ zzp lowering springs, then evolved to zzp c/o...
I'll chime in, b/c I was similar in that I wanted better performance, and to lower car slightly--but not interested in 'how low can you go'. I dont know for sure about zzp lowering springs, but from what I gather, they are ssc springs w/ monroe top plate, & KYB struts, you can do this yourself w/o zzp.
I did get c/o for my front, b/c I wanted it adjustable. ZZP c/o are manufactured by ARRAUTMOTORSPORTS.COM. ZZP is just a reseller, they sell them for same $, but get WAY over on 'shipping and handling'. So I say contact Richard @ arraut directly. You can save some $ if you get the kit. Also ZZP only has 1 spring rate, Richard has chioces at same $. ZZP uses 350 lb springs on front, which is pretty stiff for a dd, if you go directly to arraut, I might recommend 300 lb spring for front for dd.
the adjustment is a threaded sleeve, so height is ANYwhere (not stepped or incremental--completely adjustable) from more than 1" lift, to so low I could not get the jack from under my car.... The adjustable washer on the threaded sleeve is held in place w/ a common allen (hex) set screw, that's it. Height adjustment is made by turning adjuster nut by hand. Installation is easier than stock b/c coil compressor not neccessary, just thread nut down.
from what I read, m&t mnt spacers are preferred to shorter dogbones when lowering, esp if you have plans for headers. so I suggest getting new m&t mnts on general principle ($60ish for both) and spacers and install them all at same time. ZZP m&t mnt spacers are like $20, 1 of mine had hole way off. so far off, I'll say just make them yourself.
1/2" thick, 2" wide alum bar. mtr mnt is 5" long, tran mnt was 4" IIRC, but pretty sure they both could be 5". then use the mnt bolts themself to measure where to drill the holes.
If you get kit, you need rtv to hold threaded sleeve on strut body. If you get c/o, get some anti-seaze grease (permatex).
pick your height, and get an alignment.
C/o do not give the ride/comfort/quiet/feel of audi/caddy/bmw, but handling/response is there!