I have the same problem with a variation of the docking station and laptop.
I have the docking station VGP-PRZ20A and the VPCZ21S9E laptop. I need the Win8/64 bit driver.
I also download drivers for VPCZ21SHX model as the above is probably a regional one.
BTW, I also have problems with several Fn buttons that do not work (e.g. Fn F1 (mousepad), Fn F5-F6 (brightness), F9-F10 (Zoom), the Assist and Vaio buttons near the wireless switch etc.
These are all due to the fact that the laptop had initialy W7 installed and I then made a clean install of W8 and I have been struggling to get the right drivers (not all W8 drivers are available, I use some W7 ones etc..)