The Zolotarev-Schur constant is given by
(OEIS A143295), where is a complete elliptic integral of the first kind and is a complete elliptic integral of the second kind, and is the unique solution of the equation
with , namely
(OEIS A143296).
More things to try:
Weisstein, Eric W. "Zolotarev-Schur Constant." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Zolotarev-SchurConstant.html