Which two implied firewall rules are defined on a VPC network?

Implied IPv4 allow egress rule. An egress rule whose action is allow, destination is 0.0.0.0/0, and priority is the lowest possible (65535) lets any instance send traffic to any destination

Implied IPv4 deny ingress rule. An ingress rule whose action is deny, source is 0.0.0.0/0, and priority is the lowest possible (65535) protects all instances by blocking incoming connections to them.

https://cloud.google.com/vpc/docs/firewalls?hl=en#default_firewall_rules