If you accept that a native download doesn't exist, here are the three best ways to scratch that itch on your phone.
No official app exists on the Apple App Store or Google Play Store. However, the game is available for purchase on for PC. Any site claiming to offer a "direct official APK download" for mobile should be treated with caution, as these are often third-party mods or potentially harmful software. How to Play Condition Zero on Mobile counter strike condition zero download mobile