The only things you *need* on a ZX-5 to make it live really well (as good as anything out there) are the tower braces and fron hinge pivot. The stock pivot and gearbox has been upgraded by Kyosho, so that's not really much of an issue at this point.
I run mine every week...and have since they came out. I chewed one spur (78T), went to a 76T and it's been in the car for months, with no problems.
It's BY FAR the funnest car I have. I run it hard and I'm not particularly nice to it...I've broken my share of parts for sure, but that comes with the territory. I don't think I'd even consider any of the other cars out there...at least for me.
The Lazer is as fast as any of them, very tough and parts are dirt cheap (arms 4/$5, knuckles/c-hubs $5 set, chassis $25, etc.). I'm not afraid to beat it, because I can afford to fix it.
My XXX-4 cost me 40-50 bucks every time it took a good hit...LOL