Do not waste Ammo Packs early in the game. Save them for critical moments, such as buying an Infection Bomb as a zombie or a Frost Grenade when pinned down as a human.
Yes, Zombie Plague works with both Counter-Strike 1.6 and Condition-Zero. counter strike 16 zombie plague mod download link
AlliedModders is the original home of the Zombie Plague mod and remains the most trusted source. The official release threads contain both the plugin files and resources: Do not waste Ammo Packs early in the game