In your case, I think the
Velotric Discover 2 (VD) would be a better choice than the Himiway Zebra (HZ) on many fronts — despite the smaller VD battery. Details coming soon.
In fact, I'll go farther: Since you foresee mostly pavement riding, a fat tire bike like the HZ (26x4" knobbies) is the
last thing you want for your stated range goals
at your size and weight. Way too much rolling resistance for starters.
I'll explain later. Meanwhile, 2 key questions:
Q1. You haven't mentioned topography — a key factor in any range discussion. Will your target rides be mostly flat, gently rolling, moderately hilly, or even more strenuous? Will there be one or more big climbs at any point along the way?
For anything beyond moderately hilly — say, above 50 ft of elevation gain per mile on average — you should strongly consider a mid-drive instead of the hub-drives we've been discussing. On long or steep hills, your weight will be a serious challenge for a legal 750W hub-drive, with a risk of thermal shutdown or damage.
Q2. How fast does your sister's goup typically ride on this terrain? Air resistance has a big impact on range above 5 mph or so — especially for a big guy.
Finally, forget about the 75-80 mi range estimates cited for the VD and HZ. They were determined under ideal conditions with a much lighter rider. Count on your actual range on one battery being a good bit shorter. Seriously doubt that you'll get a reliable 60 mi out of one battery on either bike.