I know this is an old thread, but if you're still having problems with zip files, try peazip. It is opensource(free), and is super powerful, opening almost anything from .rar archives to .zip files, all except .alo/.aol(I forget it, but there is only 1 it can't open.
I think that is the only way you could avoid having to pay for Garritan Personal Orchestra or a similar product.What system do you run where you can't unzip a .zip file. Are you having a problem with the .7z files? The program 7zip is free. If you can't unzip .rar files with a free program called Rarzilla (it's safe) is free add unzips them. You can look up SfPack and SfArk to unpack compressed soundfonts.
Sibelius Soundsets .rar
2ff7e9595c
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