  The paper is devoted to evolution equations of the form $\partial$
$\partial$t u(t) = --(A + B(t))u(t), t $\in$ I = [0, T ], on separable Hilbert
spaces where A is a non-negative self-adjoint operator and B($\times$) is
family of non-negative self-adjoint operators such that dom(A $\alpha$)
$\subseteq$ dom(B(t)) for some $\alpha$ $\in$ [0, 1) and the map A --$\alpha$
B($\times$)A --$\alpha$ is H{\"o}lder continuous with the H{\"o}lder exponent
$\beta$ $\in$ (0, 1). It is shown that the solution operator U(t, s) of the
evolution equation can be approximated in the operator norm by a combination of
semigroups generated by A and B(t) provided the condition $\beta$ > 2$\alpha$
-- 1 is satisfied. The convergence rate for the approximation is given by the
H{\"o}lder exponent $\beta$. The result is proved using the evolution semigroup
approach.
