Hi, thanks for the question!
Zhiduo/直裰 and Daopao/道袍 are indeed very similar, and have even referred to the same thing at times. Both are traditional men’s hanfu popular during the Ming Dynasty, and comprise of a full-length, cross-collar robe with side slits beginning below the waist.
The two are differentiated nowadays by the understanding that Daopao has side panels to conceal the undergarments, while Zhiduo does not, so that the garments underneath are visible.
Here are some pictures for comparison:
– Daopao – notice how there is extra fabric on the sides to conceal the space between the slits:
Hope this helps!