On zombie maps I make a bridge-wall zombie smasher.
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p!!!!!!!!!!!!
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p = pressure plate
! = bridge raising north
You have a straight-through path with a pressure plate like to a bridge-wall (the bridge raises north or south, so the bridge is entirely "edge"). The bridge is set to low traffic [strictly speaking, this is optional since dwarves wont trigger the pressure plate if it's set to enemy, but I like on principle for dwarves to not enter death traps at all]
Dwarves (and caravans) go the long way around, but zombies, ignoring traffic designation, shamble onto the pressure plate, and due to the bridge raising delay, then get smashed by the bridge.
Normally my entry-way will have 2 or 3 such bends, each with a short-cut zombie-smasher. It's important to have some strategy for dealing with zombies which re-path while the bridge is raised, causing them to go the long (safe) way. (Another is to have the safe way also blocked off by a raising bridge linked to the same pressure plate, but this is not so good for filtering out immigrants from zombies)
To improve your chances of catching stray zombies which are chasing an immigrant (or idiot) along the entry way, include traps on the inside of corners, where they don't prevent caravans, but they catch any baddies which try to take a shortcut. The bridge walls wont ever jam and leave no mess, so are the preferred way of disposing of zombies, traps are strictly for those which somehow slip through. Cage traps are probably best because they leave no mess and you can pit the zombie into magma.
Immigrants, when they come, will normally set off the zombie camels or whatever, the zombies will chase an immigrant or animal, while the zombies are distracted, the immigrants which aren't being chased will escape into the entry way. Often an immigrant or immigrant's child or pet will end up being 'sacrificed' to the zombies since dwarves (and pets) are dumb like that, they are unable to simultaneously both run away from danger, and towards safety, so they end up being cornered.
You can improve the odds of a single dwarf being chased by zombies survival by having multiple safe underground tunnels into the fortress (i.e. in each corner of the map), each with a zombie smasher setup. You can force a dwarf to always go to the nearest safe-hole (provided they are not running from danger), by setting the entire surface to low or restricted traffic designation, this will make the pathfinder considers any path on the surface extremely undesirable, making it prefer the shortest surface path.