Meaning

Ah, the perils of the personalized lisence plate.  Your meaning, while clear to you, may not be clear to your fellow motorists.

Several times of late I have seen a large, older model Cadillac with a personalized tag reading "I AM HZ".  I never get a glance at the driver to see if it's a male or female, but this statement has at least three interpretations I can think of off the top of my head.  Four, even.

First, its the showy proclamation of faith.  The person is owned by his or her deity, presumably the Judeo-Christian one.

Second, the tag is the voice of the car, proclaiming the ownership of the driver.

Third, the driver is a woman proclaiming possession of her husband/significant other.

Then a fourth occurred to me.  Maybe someone has an electric personality and is proud of it.  Or is part of a large rental car company.