Which is a consequence of lanthanide contraction?

Size of $\mathrm{Zr}$ is approximately equal to $\mathrm{Hf}$.Because both Zr and Hf are in Periodic Table Group 4, with Hf coming after the 4f series (lanthanide). 

Because of poor f-subshell shielding, the nucleus's attraction to outer shell electrons increases, causing the size of Hf to decrease and the sizes of Zr and Hf to become nearly equal.