  One of the most famous conjecture in graph theory is Hedetniemi's conjecture
stating that the chromatic number of the categorical product of graphs is the
minimum of their chromatic numbers. Using a suitable extension of the
definition of the categorical product, Zhu proposed in 1992 a similar
conjecture for hypergraphs. We prove that Zhu's conjecture is true for the
usual Kneser hypergraphs of same rank. It provides to the best of our knowledge
the first non-trivial and explicit family of hypergraphs with rank larger than
two satisfying this conjecture (the rank two case being Hedetniemi's
conjecture). We actually prove a more general result providing a lower bound on
the chromatic number of the categorical product of any Kneser hypergraphs as
soon as they all have same rank. We derive from it new families of graphs
satisfying Hedetniemi's conjecture. The proof of the lower bound relies on the
$Z_p$-Tucker lemma.
