Keep in mind that cpdatas are data files read by ADS and zdatas are these for CAS.
The cpdata metrics are hit-based. In 12.3 and lower releases, OF decode shows only the named hits (i.e. named OF operations). The named hit gets the metrics of all hits prior to the named hit. In future 12.4, OF decode will show all hits (with arbitrary names for the unnamed hits).
The calculations for cpdata are based on the raw timestamps for each hit. The calculations for the zdata are based the aggregated metrics for the named operations. This means that during the interval, an operation name will get aggregated metrics if the operation name occurs multiple times in that interval period.