Catalyzes the ATP-dependent conversion of 7-carboxy-7-deazaguanine (CDG) to 7-cyano-7-deazaguanine (preQ(0)). 7-carboxy-7-deazaguanine + ATP + NH4(+) = 7-cyano-7-deazaguanine + ADP + H(+) + H2O + phosphate Binds 1 zinc ion per subunit. Purine metabolism; 7-cyano-7-deazaguanine biosynthesis. Belongs to the QueC family.