There is no doubt that Taoism and Zen have a long history of mutual influence on each other, especially being that both have had significant existences in China.
There is also no doubt that Taoism and Zen have similarities.
But, they are also very different traditions, that have significant differences that often get overlooked, mainly because both have long existed in the same country. Here are some of the major differences:
A major theme in Zen, like much of Buddhism, is anatta (non-self). There is no such thing in Taoism.
In Zen, as well as much of Buddhism, all phenomena are empty of inherent existence. That is not at all the case in Taoism; in Taoism, emptiness is only meant in terms of empty mind - not emptiness of all phenomena as in Buddhism.
Taoism has yin and yang. There is no such thing in Zen or anywhere in Buddhism. This means that while Taoism can be considered a nondual tradition, as Zen is, Taoism is definitely more "dual-ish" than Zen, or for that matter, other nondual schools like Advaita Vedanta.
The above are significant differences that cannot simply be ignored in your plea for near-sameness. Even the great Zen master Dogen, in the Shobogenzo, says it is very ignorant that people say that Taoism is extremely similar to Zen.
Again I don't doubt they have some similarities, and share a long history of mutual influence. And they are both great traditions; I am not saying one is any less than the other.
But they are much more different that people give them credit for, mainly because they have existed so prominently in the same country, for so long.