The factorization property of $\ell^\infty(X_k)$

Abstract: In this paper we consider the following problem: Let $X_k$, be a Banach space with a normalized basis $(e_{(k,j)})j$, whose biorthogonals are denoted by $(e{(k,j)}^*)_j$, for $k\in\mathbb{N}$, let $Z=\ell^\infty(X_k:k\in\mathbb{N})$ be their $\ell^\infty$-sum, and let $T:Z\to Z$ be a bounded linear operator, with a large diagonal, i.e. $$\inf_{k,j} \big|e^*{(k,j)}(T(e{(k,j)})\big|>0.$$ Under which condition does the identity on $Z$ factor through $T$? The purpose of this paper is to formulate general conditions for which the answer is positive.