Hello Michelle, to replace the heater matrix on the ZX, unfortunately, the dash has to come out along with the centre console, steering wheel, plastic scuttle, wiper assembly............
You need to allow at least 12 hours for the job!

And you will have screws left over.
It may also be a good time to do the water pump and thermostat. Do not forget the system needs to be flushed.
Handyman