Just downloaded Oracle Database 11g Release 2 (184.108.40.206.0) for zLinux64 file 1 (648MB) file2 (696MB), Oracle Database 11g Release 2 (220.127.116.11.0) for Linux x86 (32 Bit) file 1 (949MB) file 2 (732MB). Above the file size is correct?
The zLinux download sizes are at - http://www.oracle.com/technetwork/database/enterprise-edition/downloads/112020-zlinux64-352074.html
Each file should be at least 1G.
The x86 file sizes are at - http://www.oracle.com/technetwork/database/enterprise-edition/downloads/112010-linuxsoft-085393.html
The files you have downloaded seem to be incomplete. You will have to download them again.