You need the where command. This is one of the big differences between using search vswhere` for subsequently filtering results.
Just add this to your search:
| where cs_bytes > sc_bytes
In search the right hand side of any operator (ie =, >, <) is always assumed to be a literal value (whether or not it's in quotes) but in where unquoted strings on the right hand side are interpreted as the values of that named field.
The other huge difference of course, is that in where you can use any eval functions (ie any of the long list of functions you would more typically see in the eval command.)