(5/8)^10 : (10/16)^5 : (25/64)^4 x 128/625 =
= 5^10/(2^3)^10 : (5x2)^5/(2^4)^5 : (5^2)^4/(2^6)^4 x 2^7/5^4 =
= 5^10/2^30 : 5^5 x 2^5/2^20 : 5^8/2^24 x 2^7/5^4 =
= 5^10/2^30 : 5^5/2^15 x 2^24/5^8 x 2^7 x 5^4 =
= 5^10/2^30 x 2^15/5^5 x 2^24/5^8 x 2^7 x 5^4 =
= 2^(15+24+7-30)/5^(5+8+4-10) =
= 2^16/5^7