The Z5fd has one metering mode: evaluative. That means it can't handle backlit shots like this properly, resulting in underexposed subjects. The manual instructs you to use fill flash for situations like this, but a snapshot camera should be smart enough to meter this scene correctly.
Where did the shadows come from in this photo? They weren't there in reality, though there were some less-bright areas. Sometimes you get poor exposures like this when the image processor doesn't do sufficient correction to bring out the midtones.