RNA-binding protein that plays a role in the inhibition of multiple cellular antiviral responses activated by double-stranded RNA (dsRNA), such as inhibition of PKR activation, necroptosis, and IFN-mediated antiviral activities (PubMed:1681618, PubMed:18604270, PubMed:24257616, PubMed:25740987). Recognizes and binds Z-RNA structures via its Z-binding domain and dsRNA via its DRBM domain: RNA-binding activity is required to escape host ZBP1-dependent necroptosis (PubMed:29073079, PubMed:34192517). Mechanistically, the Z-binding domain binds Z-RNAs that are produced during vaccinia virus infection, thereby competing with Z-RNA detection by host ZBP1, suppressing ZBP1-dependent necroptosis (PubMed:34192517). Acts as a key inhibitor of the interferon response by blocking the phosphorylation and subsequent activation of IRF3 and IRF7 kinases that are required for interferon-alpha gene expression (PubMed:22419806). Inhibits NF-kappa-B activation and the ubiquitin-like protein ISG15, which is an early antiviral protein (PubMed:18604270, PubMed:24257616). The binding with host ISG15 subsequently blocks host ISGylation (PubMed:18604270, PubMed:24257616). Interacts with host G1P2/ISG15 (PubMed:24257616). Interacts with host EIF2AK2/PKR (PubMed:25740987). Interacts with host ZBP1 (PubMed:29073079). Detected at early times, by 2 hours post infection, peaks at 5 hours post infection, and decreases during the late phase of virus replication. The Z-binding domain recognizes and binds Z-RNA structures. Belongs to the poxviridae E3 protein family. Was reported to bind Z-DNA structures (PubMed:12777633, PubMed:14757814). However, it probably binds Z-RNA in vivo (PubMed:34192517).