Your hero Barksdale isnt around to suck the life out of the company so the work ZAP is off limits.
The DC 10/MD10 took the company to the next level. Not sure where you got that idea. Just like the 727 and 737 made the company start growing, the 10 eliminated the need to send multiple 27's or 37's to larger cities. The Z Van had issues but was one of the best vans I ever delivered out of. The turning radius, the side cargo door and walk thru bulkhead were a big benefit. The clutches were another subject.ZapMail was a bust. So were Z-vans, HotelPak, and MD10's, in which FedEx made a huge investment. Most are parked in the desert somewhere. They were supposed to go 20 years... oops.
A lot of these mistakes went through Smith, and he'll be around until he goes to his reward in Satan's Lair.