Many standard Java mods require a .jar file. If your browser accidentally downloaded it as a .zip , or if it is a container, you may need to extract it.
⚠️ Tell me if you are playing Java Edition or Bedrock Edition , and if you are using a mod loader like Forge or Fabric . 2️⃣ I downloaded a Custom Modpack in a .zip file Exporting Modpacks - CurseForge Support mods.zip