I didn't test that in windows command prompt but in my sync tool i'd gain best results with
--block-sync-size 4984 --db-sync-mode fastest:sync:8750
updated againupdate
It starts slowly but then outperforms defaults and size 10connection :10mbps . Although developers on github mention that the last argument lowerin the fault-proof i bet it still can be used if you wanna speed. Tool : https://github.com/alexeyneu/tool3