So how does this work? As long as I'm in my zone, I'm burning cals?
youre burning cals regardless the zone
your heart rate is in a safe zone and is effectively strengthening your heart without overly stressing it
if i were you though, i wouldnt count cals from running
the numbers are always off and will stall your cut if thats your goal
best bet is a consistent moderate deficit...that way any activity you do end up doing just gives you more weight/fat lost per week than what you may have calculated