The argument that the Z3 is universal "was an impressive party trick, but diverged entirely from the way the machine was designed, how it was actually used, or indeed from anything that would have made sense in the 1940s."
Source: ENIAC in Action p255.
> Nevertheless, the Z3 was Turing-complete – how to implement a universal Turing machine on the Z3 was shown in 1998 by Raúl Rojas.
https://en.wikipedia.org/wiki/Z3_(computer)