You need to implement the planned change for the Azure DNS Private Resolver.

Private1 is deployed with its inbound endpoint in VNet1, and an Azure DNS Private Resolver inbound endpoint can resolve only private DNS zones that are virtual-network-linked to the same virtual network where the resolver itself sits; it cannot resolve a zone just because it exists in the same subscription, or because that zone happens to be linked to a different, unrelated virtual network. Per the private DNS zone table, Zone1.com is linked to VNet1, Zone2.com is linked to VNet2, and Zone3.com has no virtual network link at all. Because Private1 ' s inbound endpoint lives in VNet1, only Zone1.com, the zone actually linked to VNet1, can be resolved through it. Zone2.com cannot be resolved by Private1 because it is linked only to VNet2, a separate virtual network with no stated peering or additional resolver configuration connecting it to VNet1; and Zone3.com cannot be resolved by any resolver in any virtual network because it has no virtual network link whatsoever, meaning no virtual network can consult it through the normal Azure-provided DNS resolution path. Extending resolution to Zone2.com would require either a separate resolver deployed in VNet2, or peering combined with a forwarding ruleset and outbound endpoint, neither of which is described as being configured here. Therefore only Zone1.com can currently be resolved.