You need to have each element (car name) in its own cell. You cannot use
conditional format to selectively highlight a portion of a cell.

The FIND() function can be used to write a formula that will put a
value in an adjoining cell if criteria is found for both, but not
conditional formatting.

For example, if cell A1 contains:
Ford, Chevy, Mazda

and cell B1 contains:
Chevy, Mercedes, Accord

You could have column C be your column for finding your matches of
Chevy, column D your column for finding matches of Ford, etc.

C1 formula could be:
=IF(AND(FIND("Chevy",A1,1),FIND("Chevy",B1,1)),"Ma tch","")


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