Mine is a translation by Man-Ho Kwok, Martin Palmer and Jay Ramsay published by Barns & Noble in 1993
The intro is nearly a book on it's own which talks about how it is arguable if there was a Lao Tzu -- Old Master, as you said. It tells of the great book burnings and slaughtering of scholars over the centuries by dictators who felt threatened by Confusion and Taoist teachings. It says the Tao Te Ching may be a compilation by many scholars over the centuries.
I will have to read thru the intro more thoroughly to see if there is a mention of the Zhuangzi
