I think they named the firmware wrong.
It should be named something like:-
ESR_HZ520_MLC_FM_HLE_2608_1x16_PLATFORM_071016.rfw
The firmware you uploaded is 2608 firmware for sure, i loaded it into Rklogoedit to check, and your player has a 2608 chip.
2608 firmware is usually about 15Mbytes and 2606 firmware is around 10Mbytes.
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