I even layer these. For example, I'll use the Dermaquest ZinClear (18% and not chalky - comes in clear and tinted) with either the Colorescience powder (when outside) layered over it or the Jane Iredale mineral makeup compact (SPF 20) (when I'm inside more).

But other sunscreens work too - you just have to read the labels under active ingredients. La Roche-Posay's Anthelios is a good mexoryl sunscreen, for example.  It comes in a moisturizing base so it is good for dry skin or dry climates. 

Then watch the spots or blotches!!! Are they darkening up less when you're in the sun??? That's the true test if you have enough on.

Is the zinc content more important than SPF?