Worth mentioning that github ended killing ZenHub, by introducing github projects, which is essentially copycat of the only useful feature ZenHub had.
GH projects also has this arbitrary distinction between notes and issues, and notes are more or less useless yet the default when adding new items to the board.
Sherlocking is a well-known risk every tenant application must consider if they want to make a business out of it.
I would hope and expect that the ZenHub folks always understood github could just integrate the features directly, and not necessarily by buying zenhub.