They have a non essential copy of the directory at the end for spoed; tools exist to rebuild it if it is corrupted from the entries inside the file. But it is usually very small (the only real life exception I met is the hvsc archive where the directory size is very significant - so they zip it again)
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So ZIPs don't have any "global" directory thing? :o
They don't have a global compression dictionary thing.
Similar effect can be achieved with gzip --rsyncable, which IIRC resets the dictionary based on a rolling sum.
They have a non essential copy of the directory at the end for spoed; tools exist to rebuild it if it is corrupted from the entries inside the file. But it is usually very small (the only real life exception I met is the hvsc archive where the directory size is very significant - so they zip it again)