When I rebuilt the loom on my T16 conversion after the mess zippy made I noted the wiring colours and posted them on my website -
http://home.btconnect.com/talkingcar...engineloom.htm
The colours are different on the different models but the functions are the same, you'll just have to identify the colours in the looms you are using to get a start.
Just to further complicate matters the cars I used were both dizzy and you are working with wasted.
IIRC the actual feed to the speedo on the ZS comes from the ABS ECU which in turn takes the info from the wheel sensor. If you are using the 400 dials you will need the sensor from it's gearbox, this is different to the Ti.
Not sure how you cruise control works but if it is like the system on the KV6 which uses the same engine bay components there will be a couple of control modules and lots of wiring in the loom so this might sway me to use that loom as much as possible.
Have you taken the exhaust off the 400 or are you using the one from the Ti?
I would be tempted to take the door cards from the 400, especially if the ones in the ZS don't have the colour panels. Also the rear winders and looms are worth taking as you'll be able to sell them.