Following is the series of reaction that takes place.

$CFC{l}_{3}Cl+C^{.}FC{l}_2$  (In this step, chloroform breaks into chlorine and a $C^{.}FC{l}_2$ radical.)

$C{l}^{.}+O_{3}Cl{O}^{.}+O_2$  (In this step, the chlorine radical reacts with ozone to form oxygen and ClO radicals.)

Further, the ClO radical reacts with O to form even more chlorine radicals and oxygen, thereby contributing more to the conversion of ozone to oxygen. Thus, the chlorine radical reacts with ozone to form oxygen.