What is the use of Isodiaphers and Isosters?

Isodiaphers are the atoms for which the difference between the number of neutrons and number of protons is the same. So if X is the neutron number and Z is the proton number, then atoms having same value of (X-Z) are the isodiaphers.
for example
⁹⁰Th₂₃₄ and ⁹²U₂₃₈
in thorium proton number is 90 and neutron number is 144
144-90 = 54
in uranium proton number is 92 and neutron number is 146
146 - 92 = 54

Isosteres are molecules or ions with the same number of atoms.
Some examples of isosteres include:-
Sodium and hydrogen cations
Carbon dioxide (CO2) and nitrous oxide (N2O)

--►Since there is either same difference of neutron or proton or same number of atom in isodiaphers and isosteres respectively. It leads to some common characterstics between these elements. And It also helps in categorisation of these elements easily.