Role of zinc chloride in reaction of ether
I think that it reminds Fischer esterification at the beginning. Zinc dichloride acts as a Lewis acid by coordination at the carbonyl oxygen in AcCl. It activates C=O bond because of larger contribution of carbocation form. And this cation undergoes coordination of Et2O with formation of zwitterionic tetrahedral intermediate. This particle eliminates our catalyst and cloride-anion. The product of this step is acetyl diethyl oxonium. Cloride-anion is quite nucleophilic, but we have an excellent leaving group without charge (AcOEt), so Sn2-reaction occurs and lead to the final products