Hi, I thought this when I added a 32gb SD card. It just didn't recognise it. So I thought maybe you can only use small SD cards, so I tried a 2gb one and it worked. So some expandable storage does work but you can't bang a 64gb card in and expect it to work.
I had no trouble using a 32gb SD card to my Z3C. I used a Sandisk Extreme micro SDHC U1 card (now they're available as U3) for less than $20 on Amazon.