how is big mom didn't take any damage, she screamed pretty loudly when law attacked her with counter shock, also kid and law damage doesn't remotely come close to luffy and zoro, they just took some elemental attacks that does relatively low damage, and some easily survivable attacks.
also we mustn't forget that zoro's recovery is on a timer, so he won't be fighting forever.so luffy's glory is still preserved.
king was shown bleeding just from two basic attacks from marco, so he doesn't come close in durability to kaido, zoro has proven to do serious damage even overpowering kaido with some attacks, it'll be very underwhelming if he struggled against an king that wasn't even able to defeat marco.