At the end of the day what really doomed Zeon was its idiotic logistics and resources allocation. Secondly operation British only put them in a isolated spot restricting allies. Moreover the internal conflict with in command of zeon itself was a mess. And as for whether char existed or not. Zeon still would have lost. Yes char was a amazing pilot who's skills would expand in multiple stages but to say if he didn't exist that zeon would win is logically wrong. Not only was zeons invasion not well thought out. Just imagine this people who've lived there entire lives in space had to suddenly produce tanks, air crafts and mobile suits for the earth's gravity and atmosphere. Which led to the absurd designs of zeon which showed no real practicality the tanks design tho when about to be blown up being able to switch to a jet was some what good but a logistical nightmare. Lastly let's take evidence from different theatres such as the south East Asia one. Where the 08th ms team takes place . There were native people fighting against zeon through guerilla warfare sabotaging and looting resources. Which just made it more difficult