That's because the 452s are only marginally better in the wet than the 040s, and they're both not really suitable for the Zed and this is what happens when you mix tyres.
Oh come one, this has been going for pages now and that's the first time I've mentioned anything!
Hope it gets sorted out soon fella, I think you took it quite well considering but please don't underestimate how important it is to have matching tyres all round.
No its not.