In Ontap 9.2P1 when I run a "net route show" and "net route show-lifs", it has 0.0.0.0/0 as a destination for all interfaces. Should this be changed to a specific address or is this the default and recommended entry?
that is the default route, just means "anywhere". You can add your own routing table entries as needed.
If you have multiple default gateways, make sure you use differnet metrics. There was a bug at one point, that caused issues if you have multiple gateways with the same metric (the default I believe is each will default to 20)