If I recall correctly, the fanime is called “A Summer’s Day Dream”.
Also, it wasn’t shut down by ZUN, per se, but it was originally called “Touhou Anime Project”, and ZUN said on his blog that with the high-profile voice actors in this, it could be mistaken for an official Touhou product when it wasn't.
In a nutshell, this fanime is so professionally made that the creator of the source series had to flag it down, saying "This ain't official stuff".