Why Zr and Hf exhibit similar properties ?

Explanation

Both `Zr and Hf` belong to the `4^(th)` group
As such they have similar outer electronic configuration and hence similar chemical properties further due to lanthanoid contraction they have similar atomic radii and hence similar Physical properties.
`{:("Element ","Atomic radii"),(Zr, "160 pm"),(Hf ,"159 pm"):}`