How did Gecko Moria created marine zombies in Marine War without Hogback around?
Hogback was useful for Moria, because he could stitch together different parts of separate bodies, thus  only using the strongest parts of those bodies. The best example for this is Sanji's zombie. He is essentially a penguin, but instead of the useless mouth, hogback replaced it with a dogs jaw.

If you look at the marine zombies, none of them has a dog head or bear hands. The closest to this category is the centaur on the left, but that's..."normal". A normal marine doctor should be able, to fix those bodies up.