A zonal isolation assessment system comprising: a receiver residing at or near a surface of a wellbore; a processor communicatively coupled to the receiver; production tubing configured to be disposed in the wellbore; a zonal isolation assembly configured to reside downhole of and fluidically coupled to the production tubing, the zonal isolation assembly configured to isolate a zone of the wellbore and comprising: isolation tubing configured to flow production fluid from the wellbore to the production tubing, a first sealing element coupled to the isolation tubing, and a second sealing element coupled to the isolation tubing and disposed downhole of the first sealing element, the first sealing element and the second sealing element configured to be set on a wall of the wellbore to fluidically isolate an internal volume of the isolation tubing from an isolated annulus defined between the isolation tubing and the wall of the wellbore, the annulus extending from the first sealing element to the second sealing element; and an assessment assembly disposed at least partially inside the isolation tubing and communicatively coupled to the receiver, the assessment assembly comprising: a first pressure sensor residing at the internal volume of the isolation tubing and configured to sense first pressure data representing a fluidic pressure of the internal volume over time, and a second pressure sensor residing at the annulus and configured to sense second pressure data representing a fluidic pressure of the annulus over time, the assessment assembly configured to transmit, to the receiver, the first pressure data and the second pressure data; wherein the processor is configured to determine, based on a rate of change over time between the first pressure data and the second pressure data, a level of zonal isolation integrity of the zonal isolation assembly. a receiver residing at or near a surface of a wellbore; a processor communicatively coupled to the receiver; production tubing configured to be disposed in the wellbore; a zonal isolation assembly configured to reside downhole of and fluidically coupled to the production tubing, the zonal isolation assembly configured to isolate a zone of the wellbore and comprising: isolation tubing configured to flow production fluid from the wellbore to the production tubing, a first sealing element coupled to the isolation tubing, and a second sealing element coupled to the isolation tubing and disposed downhole of the first sealing element, the first sealing element and the second sealing element configured to be set on a wall of the wellbore to fluidically isolate an internal volume of the isolation tubing from an isolated annulus defined between the isolation tubing and the wall of the wellbore, the annulus extending from the first sealing element to the second sealing element; and isolation tubing configured to flow production fluid from the wellbore to the production tubing, a first sealing element coupled to the isolation tubing, and a second sealing element coupled to the isolation tubing and disposed downhole of the first sealing element, the first sealing element and the second sealing element configured to be set on a wall of the wellbore to fluidically isolate an internal volume of the isolation tubing from an isolated annulus defined between the isolation tubing and the wall of the wellbore, the annulus extending from the first sealing element to the second sealing element; and an assessment assembly disposed at least partially inside the isolation tubing and communicatively coupled to the receiver, the assessment assembly comprising: a first pressure sensor residing at the internal volume of the isolation tubing and configured to sense first pressure data representing a fluidic pressure of the internal volume over time, and a second pressure sensor residing at the annulus and configured to sense second pressure data representing a fluidic pressure of the annulus over time, the assessment assembly configured to transmit, to the receiver, the first pressure data and the second pressure data; wherein the processor is configured to determine, based on a rate of change over time between the first pressure data and the second pressure data, a level of zonal isolation integrity of the zonal isolation assembly. a first pressure sensor residing at the internal volume of the isolation tubing and configured to sense first pressure data representing a fluidic pressure of the internal volume over time, and a second pressure sensor residing at the annulus and configured to sense second pressure data representing a fluidic pressure of the annulus over time, the assessment assembly configured to transmit, to the receiver, the first pressure data and the second pressure data; wherein the processor is configured to determine, based on a rate of change over time between the first pressure data and the second pressure data, a level of zonal isolation integrity of the zonal isolation assembly.