ZEnith was actually used by some telcos for an early version of toll-free calling - before the days of 800 numbers, you could dial the operator and ask for "ZEnith XXXX" and be connected to a business, usually somewhere outside the local calling area, that was willing to pay for that privilege. You couldn't direct-dial those numbers. In some areas, these were "Enterprise" numbers. I think "Zenith" may also have been used for early mobile phones...and in fact, maybe that's all that "Zenith" was, while it was "Enterprise" that was toll-free.