We moved from UPS to DHL as the former was having a Brexit nightmare with exports.
DHL labels print, but a bit on the small side. I think they are designed to be printed at 4" x 8.5" rather than 4" x 6". It hasn't caused a problem yet but the addresses are pretty tiny after our (Zebra ZD420) printer scales it.
Can you please add a 4" x 8.5" label size?