thus restore should work with:
for i in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21; do mtd write /mnt/zte-mf286d/mtd$i /dev/mtd$i; done
BTW: For connecting the router when Linux/Busybox is running, you have to use LAN2, WAN/LAN1 is not working, the tftp works with both ports.
regards thg