YEah, there is a mess of vacuum lines under the dash. You could try pulling the lines out, one by one, inspecting and replacing. There is alimited number that you can get to, but if you pull a couple of panels from the underside of the dash (couple of screws here and there) you can get to more. You might get lucky and find a broken or cracked hose in a place that's accessible.
By doing it one hose at a time, you will not have a problem with putting them back wrong. It's a b!tch job, but it may save you tons of $$ if you can find it yourself. Think of it....if the mechanic finds a cracked hose in an easily accessible place, don't you think that he may fix it in 5 minutes...park the car for a couple of days, then charge you $800 for the work.....nah, not a mechanic...they are very reputable....like used car dealers
Also, maybe walk around a couple of junk yards and see if you can find a ZX with the dash removed. Then you can get a good look at where all the lines are.
Tim