1/16*(2a+1)(2a-1)(a^4+1/16)(4a^2+1)
=(1/16)*(a^4+1/16)(4a^2+1)(4a^2-1)
=(1/16)*(a^4+1/16)(16a^4-1)
=(a^4+1/16)(a^4-1/16)
=a^8-1/256