Not really. It was in CP, which became GT2, which is a much faster class than EP. But those cars were allowed more modifications, so they had more hp and chassis modification options than the EP cars. An old, properly sorted GT2 car "should" spank an EP car. ITS is a slower class than EP, and when Z's race in ITS they are allowed significantly less modifications, but they're racing with against BMW 3 series that simply have better suspension designs and stronger motors. I suppose ultimately the Z has been relegated to slower and slower classes in that it doesn't compete in GT2 anymore, but what it does compete well in is based on how much modification can be done.
Or to say another way, the Z can be slow in a slow class or faster in a fast class, it all depends on what modifications are allowed. The rules determine whether or not it is competitive, not the age of the car.