A quick (and probably flawed) summary of Zone 2 training: Zone 2 is also referred to as base training. It is a pace that one might do for 45 minutes to an hour 3-4 times per week. It is effective for training aerobic fitness.
I have heard from two authorities for where Zone 2 is with respect to predicted heart rate. You can use the Miller equation, which is 200 - .48 * age to find a prediction of heart rate that has been shown to be affective in obese and overweight people.† The most recent is Peter Attia, who puts it at about %70 to %80 max heart rate.†† Going back a bit farther to a coach I really trust, he was proscribing workouts both in the 70-80% range and in the 80-90% range. The latter zone might be something higher than Zone 2 training.
[Edit: On further reflection, I'm tempted to break Z2 up into Z2a and Z2b, 65-70%MHR and 70-75%MHR.]
This is a post where I really recommend consulting with a physician and/or cardiologist before trying to reach the heart rate targets below.
† Franckowiak, Shawn C., et al. "Maximal heart rate prediction in adults that are overweight or obese." Journal of strength and conditioning research/National Strength & Conditioning Association 25.5 (2011): 1407. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3081386/).
†† MD, Peter. "#201 – Deep dive back into Zone 2 | Iñigo San-Millán, Ph.D. (Pt. 2)". Peter Attia MD, Iñigo San-Millán, Ph.D. 3/28/2022. https://peterattiamd.com/inigosanmillan2/
