The income of Priya is $40\%$ higher than that of Liza and the income of Disha is $20\%$ less than that of Liza. Income of Priya is higher than income of Disha by:

Let the income of Liza be $100$.
* Priya's income is $40\%$ higher than Liza's:

$$\text{Priya’s Income}=100+\left(\frac{40}{100}\times 100\right)=140$$

* Disha's income is $20\%$ less than Liza's:

$$\text{Disha’s Income}=100-\left(\frac{20}{100}\times 100\right)=80$$

We need to find how much higher Priya's income is compared to Disha's income:

$$\text{Difference}=140-80=60$$

The percentage increase relative to Disha's income is:

$$\text{Percentage}=\left(\frac{\text{Difference}}{\text{Disha’s Income}}\right)\times 100$$

$$\text{Percentage}=\frac{60}{80}\times 100=\frac{3}{4}\times 100=75\%$$

Thus, Priya's income is higher than Disha's by $75\%$.