Going to change all 4 as I have a roofing nail in one of my tyres and they changed the tread pattern on the uniroyals I have on there.
My wheels are mag slots front 185/70/r14 rear 195/70/r14.
The tyres on the car have been on there for over 5 years anyway as previous owner hadn't used it so I think it's worth changing anyway. Plus I personally wouldn't want to trust a repair on a tyre and not many tyre places do it any more.
I run Michelin Pilots on mine, very good all rounder for road use and progressive on limit/in the wet.
I run the same on the daily drivers and have done for 7 years as I find them excellent in other ways such as road noise, wet/dry braking, wear, feel etc.
Also probably not relevant to your Z but for info, I run the continental TS830p for winter months and cannot recommend highly enough!!! Stunning on standing water + last year I was leaving Range Rovers and X5s on snow covered hills in my front drive diesel Audi wardrobe on wheels. On snow and ice they are exceptional for hill starts and general traction!!