symmetric monoidal (∞,1)-category of spectra
The Eilenberg–Zilber operad $\mathcal{Z}_k$ is the endomorphism operad of the chain complex of chains on the standard $k$-simplex.
By the method of acyclic model?s by Eilenberg and Zilber, one shows that $\mathcal{Z}(\infty)$ is an E-∞ operad (therefore the name).
See the references at cochains on simplicial sets.