What is an important difference between Tawaf al-Qudum and Tawaf al-Ziyarah?

Book of Hajj: Entering Mecca and Tawaf al-Qudum

• Both are always voluntary
• Qudum is Sunnah; Ziyarah is a required pillar of Hajj
• Ziyarah is forbidden to Meccans
• Qudum is another name for saʿy