Let π : E → B be a fiber bundle with fiber having the mod-2 cohomology algebra of a real or a complex projective space and let π ′ : E ′ → B be vector bundle such that Z2 acts fiber preserving and freely on E and E ′ − 0, where 0 stands for the zero section of the bundle π ′ : E ′ → B. For a fiber preserving Z2-equivariant map f : E → E ′ , we estimate the cohomological dimension of the zero se...