I've read that Zone 2 helps with fat burning efficiency. I notice that I'm not quite as hungry after a Zone 2 session.

I found it very difficult to stay in Zone 2 outdoors, with rolling hills. Some definitions of a Zone 2 workout are at a higher effort level than the 7 heartrate zones definition of Zone 2, though.
One simple test is to recite the whole alphabet out loud on one breath -- that's a good indicator for me, matching with my powermeter watts range for Zone 2.
Zone 2 starts out "way too easy", but at the end of a 90 minute trainer session, I feel it in my legs.

A Zwift workout is fantastic for Zone 2 riding. It sets a watt target, and keeps the trainer within 5 watts of that as long as I keep pedaling fairly steadily. I can ride in the Zwift terrain, even on steep climbs -- my simulated speed just drops way down. Nice!