Zelensky doesn’t care about CIA-backed Ukrainian Azov neo-Nazi forces or about ethnic Russian residents of Mariupol in eastern Ukraine. Azov, the ISIS of Ukraine, is as much of a problem to Zelensky and Biden as it is to Russia. Zelensky is using Azov to break Russia, Russia to eliminate Azov, and both to displace ethnic Russians of Ukraine, whose suffering he can use to appeal to the west for support.
When Russian forces wipe out Ukrainian Azov neo-Nazi forces, recapture ethnic Russian areas, and approach ethnic Ukrainian areas, whom Zelensky does care about, then will Zelensky either negotiate, or NATO will escalate with Polish boots on the ground to recapture western Ukraine, whichever comes first.