Problem downloading firmware to device with dfu-util

Hi, I'm trying to use linux to update the SDC21xxS firmware. I can use minicom to put the device into DFU mode, and then can upload and read the firmware from the device with dfu-util. I've tried to download the SDC21xxS firmware files (.zdfu and .zbin) to the device but both files have failed. I do not have much experience with DFU, STM or Roboteq devices, so I would be grateful for any help.
dfu-util -v -D SDC21XXS-Firmware-Update-v18d-010818.zdfu
dfu-util 0.8

Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc.
Copyright 2010-2014 Tormod Volden and Stefan Schmidt
This program is Free Software and has ABSOLUTELY NO WARRANTY
Please report bugs to dfu-util@lists.gnumonks.org

dfu-util: Invalid DFU suffix signature
dfu-util: A valid DFU suffix will be required in a future dfu-util release!!!
Opening DFU capable USB device...
ID 0483:df11
Run-time device DFU version 011a
Claiming USB DFU Interface...
Setting Alternate Setting #0 ...
Determining device status: state = dfuIDLE, status = 0
dfuIDLE, continuing
DFU mode device DFU version 011a
Device returned transfer size 1024
DfuSe interface name: "Internal Flash "
Memory segment at 0x08000000 8 x 2048 = 16384 ®
Memory segment at 0x08004000 120 x 2048 = 245760 (rew)
dfu-util: Only DfuSe file version 1.1a is supported
dfu-util: (for raw binary download, use the --dfuse-address option)