First converts r to z' for each correlation. Then constructs a z test for the difference
z <- (z1 - z2)/sqrt(1/(n1-3)+1/(n2-3))
References
Cohen, J., Cohen, P., West, S. G., & Aiken, L. S. (2003).
Applied multiple regression/correlation analysis for the behavioral sciences (3rd ed.).
Mahwah, NJ: Lawrence Erlbaum.