I think the answer to this is that it would cost more...to the point where you might as well just buy a new tram. Which they can't because they had to pay a billion to get out of the tunnel contract.
The process of chopping off the ends is theoretically cheaper. The Zs might be stuffed, but so were the Konstals before renovation.
Mind you, I'm not advocating this, rather pointing out that others are doing it to comply with accessibility requirements. There may be perfectly good technical and financial agreements why it can't be done in Australia. However, I would rather these than Citadis 302 in Adelaide any day. Of course, I'd rather almost any rotating bogie car than the Citadis....

Sent on the go with Vodafone

-------- Original message --------
From: "transitclassics@iinet.net.au [TramsDownUnder]" TramsDownUnder@...>
Date: 13/08/2018 1:00 AM (GMT+01:00)
To:TramsDownUnder@...
Subject: [TramsDownUnder] Re: OT Busy times at Central - ZRH

I note comments on the other site about converting Z's by chopping ends off and inserting new centre sections etc, why not do it properly? Pull out the plans for what the last 30 B's were supposed to be (they would have been the C class) and build entirely new bodies (the bodies on the Z's are pretty stuffed, never having had an overhaul) to the 70% low floor design. Re-furbish the trucks and control package (even use the panto!)  and you could possibly re-cycle other parts like doors and seating. You would need to add one un-motored truck like one of the E class centre trucks) and have just the one articulation. This would give you a tram, suited for the lighter lines without the need for upgrading power supply and they would cost about half the cost of a new tram, they could be built at Dandenong to keep that workforce in place and be better than trying to make a purse out of a pigs ear by just refurbishing the Z3's and A's.