From LQWiki

zless

"zip+less" (see the less command for more on this.)

Linux/Unix command, companion to zmore.

Lets you read compressed text files, one screenful at a time, without extracting them first. (Will also read uncompressed text.) Equivalent to setting the PAGER environment variable to less and running zmore.

The familiar more command also does this, but only with uncompressed files.