совершенно случайно наткнулся на АПИшные функции работы с зипами ))
The following functions are used to decompress files that were compressed by the Lempel-Ziv algorithm.
Function Description
GetExpandedName -Retrieves the original name of a compressed file.
LZClose -Closes a file that was opened by using LZOpenFile.
LZCopy -Copies a source file to a destination file.
LZInit- Allocates memory for the internal data structures required to decompress files, and then creates and initializes them.
LZOpenFile -Creates, opens, reopens, or deletes the specified file.
LZRead -Reads (at most) the specified number of bytes from a file and copies them into a buffer.
LZSeek -Moves a file pointer a number of bytes from a starting position.
сам не пробовал, тему создал для застолбления в памяти - чтобы при случае опробовать
