Is titanium dioxide as good as zinc oxide?

Roughly equivalent: They are roughly equivalent as sunscreens but the preparation will have a lot to do with the effectiveness.

Zinc Oxide more: Both titanium dioxide and zinc oxide are natural physical sunscreens. Tio2 provides protection from uvb and short uva radiation only, while zinc oxide provides comprehensive uvb and short and long uva protection. Many sunscreen products use a combination of these two, along with antioxidants to give you optimal protection for use. Use of an antioxidant sunscreen daily is critical to skin health.