Zeta4 denotes Zeta[4].
Zeta4
Zeta[4]
Overview, Zeta2, Zeta6, Zeta8, Zeta10.
ζ(4)\zeta (4)ζ(4)
N[Zeta4]
1.082321.082321.08232
SimplifyPolyLog[Pi^4]
90ζ(4)90 \zeta (4)90ζ(4)
Conjugate[Zeta4]