Get rid of those awful awful tyres immediately. Before the ditch finders do as their name suggests. Or worse.
Either get some Bridgestone RE050s to match the front, or ideally replace the whole set. I'd suggest Falken FK 452.
Good advice
Have any of you experience of Maxxis Ma-Z1 tyres?
There is a "Drift" variant of the MA-Z1 which is not as good as a road tyre as the "standard" MA-Z1, unfortunately it was the Drift variant which autoexpress tested (and it rated it above some premium contenders):
So, they are not as good as the bridgstones, but they aren't ditch finders. I bought some replacement alloys for my Z that had "sunway" tyres on - these were truly dreadful and true ditchfinders causing the car the slide around in the wet - they didn't last long.
So I would suggest the OP gets their alignment checked (inc castor / camber) by a reputable motorsport place. Alignment is critical on a performance car like a Z.
I would check all the suspension bushings (bannana bar etc) as these so crack and cause alignment to shift.
Check the date code of tyres - I would replace after 7 years on a road car as they do "go off".