I new in ZCASH, and read the blog https://blog.z.cash/snark-explain/

It say:

when p is large, given an element h in Z∗p it is difficult to find the integer a in 0,…,p−2 such that ga=h(modp).

Why? g0=1,g1=2,so a=h-1.

As ”exponents add up when elements are multiplied”, we have for a,b in 0,…,p−2 ga⋅gb=ga+b(modp−1).

I don’t understand this.