Powers in the first bracket range from 0 to 4 while in second bracket include 0, -2, -4, ..., -12
Hence to get a constant we can multiply both powers of 0 or a power of 2 and -2 or 4 and -4:
Constant term = 4C0x6C0 + 4C2(2x)^2*6C1(-1/x^2) + 4C4(2x)^4*6C2(-1/x^2)^2
= 1 - 144 + 240
= 97
Hope...