Is there multi-core/multi processor/multi-thread support?

Yes. It is possible to enable the use of multiple threads when zipping with the Deflate or Deflate64 compression methods.

You can find more details in the documentation here:
https://doc.xceed.com/xceed-filesystem-for-net/webframe.html#topic169.html

Does it occupy more temp space?

In most operations, temporary files are not used. This keeps performance high and the required disk space low. These operations include: zipping into a new zip file, adding new files into an existing zip file, updating meta data of an existing zip file and all unzipping operations.

The component uses temporary files only when absolutely necessary. These operations include: updating an existing file in an existing zip file. Deleting an item in an existing zip file.

Does it handle file transfer?

Xceed Zip for .NET itself does not have file transfer functionality. However, it can read and write files located on Windows network drives that are normally available via Windows Explorer. Also, Xceed Zip for .NET can be paired with our Xceed SFtp for .NET and Xceed Ftp for .NET component. You can then transfer or receive your zip files via the SSH/SFtp and/or FTP protocols via a shared API.

You can find an example of this in the documentation here:
https://doc.xceed.com/xceed-filesystem-for-net/webframe.html#topic298.html

Do you have an encryption module in this?  What type of encryption is available? Is it secure ? Please provide us with detailed info on encryption type.

Yes. We support two different encryption methods in zip files:

• Compatible: The traditional ZIP encryption. This is a weak encryption method.
• WinZipAes: The WinZip AES encryption method. This is a strong encryption method.

You can find more detailed descriptions of the encryption methods, including when you should use them and links to detailed technical information of the encryption algorithms  in the documentation here:
https://doc.xceed.com/xceed-filesystem-for-net/topic9308.html

You can also find code examples of zipping and unzipping with AES here:
https://doc.xceed.com/xceed-filesystem-for-net/webframe.html#topic168.html

Finally, Xceed Zip for .NET allows your application to use alternative implementations of the AES encryption depending on your scenario, for example if you are only running on recent versions of Windows or wish to use the fastest AES implementation at the expense of compatibility. You can find more details here:
https://doc.xceed.com/xceed-filesystem-for-net/webframe.html#topic165.html