State of the art in zero knowledge proof compilers? What is the current state of the art zero knowledge  proof compiler ? I need one that can minimally handle double exponentiation  by a known value  E.g.

$$Pok\{(\alpha):h=g^{\alpha^b}\} $$ 
where b, g and h are public but $\alpha$ is secret. 

Preferably it should be able to handle double discrete log proofs E.g.

$$Pok\{(\beta):h=g^{a^\beta}\} $$ where a, g and h are public and $\beta$ s secret.

ZKPDL does not handle at least the later case.
A protocol for double discrete log proofs is given in M. Stadler, "Publicly verifiable secret sharing", Eurocrypt '96, Section 3.3.

In Stadler's notation, given $g$, $y$, and $V = g^{y^\alpha}$, and $A = h^\alpha$ for some generator $h$, Stadler's protocol shows how to prove that $\log_h A = \log_y(\log_g V)$. Now, to solve your problem, let $V$, $g$, and $y$ be known. To prove knowledge of $\alpha$, have the verifier choose a generator $h$. The prover provides $A = h^\alpha$ and uses Stadler's protocol to prove that $\log_h A = \log_y(\log_g V)$.