This was my question too. Zapcc's faq says: Precompiled headers requires building your project to the exact precompiled headers rules. Most projects do not bot

This was my question too. Zapcc's faq says: Precompiled headers requires building your project to the exact precompiled headers rules. Most projects do not bother with using precompiled headers. Zapcc works within your existing build. Precompiled headers are currently ignored by Zapcc.