Now looking at definitions starting with letter "z"
Z : The symbol for impedance.
zenith : Another word for tangency.
zero frame : The first frame of a roll of film or video tape, appropriately numbered 00:00:00:00.
zero return : A control on a tape recorder which will automatically stop the tape on rewind when the tape counter reaches zero.
zero- level : A level of 0dB(V). All measurements are made relative to this level as it represents (in properly calibrated equipment) the optimal recording or broadcast level. Higher signal levels than this indicate the possibility of overmodulation. Significantly lower levels than this indicate the possibility of undermodulation. See decibel, operating level.
zero-crossing : The point in a sample where the waveform reaches zero amplitude. When editing a loop, it is usual that both the beginning and end points of a loop are at a zero crossing. However, zero crossings are not important if the beginning and end points of the loop are at the same signal level and have about the same waveform slope. The harmonic content of the wave in the region around the loop point has much more effect on the quality of the loop than whether the loop point is at a zero-crossing.
zero-locate : See autolocator."
zone : See split point.