When you have a networked attached drive and unzip files on it, you're copying the zipped file across the network to the computer, decompressing it on the computer, and copying the uncompressed files back across the network to the drive. Unless you have a very fast network, this is an inherently slow operation.
Can you download the files to the local laptop drive and then unzip them to the networked drives? That'll save you one direction worth of traffic, anyway.
EDIT: Also obviously anything you can do to maximize networking speed (e.g. plugging in an ethernet cable) while you're doing large data transfers will help.
