Optimizing a function with 2 variables with matrix form

Question

Someone else asked a question, I've been thought a lot, but still have no ideas. Could someone give me some advice about question below? $$ \min_{X,Z\in S^{++}}||-nZ+XA+B||_F^2 $$ $$ s.t \quad XZ-I=0, ZX-I=0 $$ where,$X,Z$ are variables. $S^{++}$ means positive definite matrix, and $A$ is a diagonal matrix, $B$ is a symmetric matrix, $n>0$ is a constant number.