The idea to join the Companions only came to J’Zhirr a few days later.
At that moment, all J’Zhirr could do was to stare open-mouthed at Aela the Huntress after she called this one a milk drinker. J’Zhirr could not even think of a fitting retort back. This one had to admit there was something amounting to awe as he watched She-Who-Just-Killed-A-Giant coolly walked away. Although at the same time, J’Zhirr also thought that she was very rude.
Of course, J’Zhirr remembered to search the fallen giant’s corpse afterwards. Nothing goes to waste.