Pattern match 0 value

I have some cpus that fail and I want to capture which one does.

In logs I see an update ev minute

11/03/2021 23:10 A: 100mhz B: 100mhz C: 0mhz

The output here should be C as I want to capture and count every time AB or C = 0

Would be even better if I can capture and count if more than one cpu is at 0

Say for example A,B as the output.

Thanks in advance!