Cheaper to own...

I see a lot of ZT vs tractor discussions, but nothing about cost of ownership. Initial purchase aside, which one costs more to over, overall? Consider fuel, maintenance, replacement parts, service work, parts availability, etc..

Which one is more economical to own, and how much sacrifice am I making for that cost savings? I'm not looking for opinions on which is better or does what.. Just overall cost of ownership, which one turns out to be more economical?

3.5acre mostly opened grass surround by woods. Not many obstructions. No grades or hills, but pretty uneven/bumpy. Area requires twice a week mowing.