  We prove that the 2-hermitean matrix model and the complex-matrix model obey
the same loop equations, and as a byproduct, we find a formula for
Itzykzon-Zuber's type integrals over the unitary group. Integrals over U(n) are
rewritten as gaussian integrals over triangular matrices and then computed
explicitly. That formula is an efficient alternative to the former
Shatashvili's formula.
