As Mr Zelensky looked on and sang the national anthem, the Ukrainian flag was raised in front of the burned-out city hall building.
After almost six months under Russian occupation, Izyum was left largely devastated, with apartment buildings scorched by fire.
A gaping hole and piles of rubble stood where one building had collapsed.
“The view is very shocking, but it is not shocking for me,” Mr Zelensky said.
“We began to see the same pictures from Bucha, from the first de-occupied territories. The same destroyed buildings, killed people.”
Bucha is a small city on the outskirts of Kyiv that Russian forces withdrew from in March. In the aftermath, Ukrainian authorities discovered the bodies of hundreds of civilians dumped in streets, yards and mass graves. Many bore signs of torture.
Prosecutors said they so far have found six bodies with traces of torture in recently retaken Kharkiv region villages.
The head of the Kharkiv prosecutor’s office, Oleksandr Filchakov, said bodies were found in Hrakove and Zaliznyche, villages around 60 kilometers (35 miles) southeast of Kharkiv city.
“We have a terrible picture of what the occupiers did. ... Such cities as Balakliia, Izyum, are standing in the same row as Bucha, Borodyanka, Irpin,” said Ukrainian Prosecutor General Andriy Kostin, listing the names of places where the Ukrainians have alleged Russian forces committed atrocities.
Local authorities have made similar claims in other areas previously held by Russia, but there is not yet evidence of this.
Moscow’s recent rout in northeast Ukraine was its largest military defeat since the withdrawal of Russian troops from areas around Kyiv, the Ukrainian capital.
On the northern outskirts of Izyum, the remains of Russian tanks and vehicles lay shattered along the road.
As Zelensky visited, his forces pressed their counteroffensive, demined liberated territory and investigated possible war crimes. He said that as Ukrainian soldiers retake occupied villages, “the life comes back”.