He didn't have the Kamui in part 1 yet he defeated Zabuza and don't forget he made it jonin before he got his Sharingan and invented the Chidori
Kakashi had kamui since rin death but he didn't use it until part2.
Without sharinghan kakashi will definitely lose against zabuza.
If naruto and sasuke didn't help kakashi here then kakashi will be dead for sure.
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He defeated zabuza because he copied zabuza's ultimate jutsu by using sharinghan so your whole point is invalid.
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Zabuza >>> current kakashi ..