"Emotions have run high today. But it is good that 5 countries met to bring peace closer," Zelenskiy wrote on the X social media platform.
"The American side shared its vision. Ukraine and other Europeans presented their inputs."
He pledged Ukraine would always abide by its constitution and said he believed Ukraine's partners, including the United States would act will "act in line with its strong decisions".
This appeared to be an oblique reference to US criticism of Zelenskiy's statement that recognition Russian control over the Crimea peninsula would be against Ukraine's constitution.
US President Donald Trump's Ukraine envoy Keith Kellogg called the peace talks in the United Kingdom aimed at ending the three-year war, which included Zelenskiy's chief of staff Andriy Yermak, positive.
"It's time to move forward on President Trump's UKR-RU war directive: stop the killing, achieve peace, and put America First," Kellogg said in a statement on X.
The UK government said the talks - including the Ukrainian delegation and officials from the US, France and Germany - made significant progress towards a common position.
"The talks today were productive and successful, and significant progress was made on reaching a common position on next steps," a foreign office spokesperson said in a statement.
"All agreed to continue their close co-ordination and looked forward to further talks soon."
Zelenskiy on Tuesday reiterated that Ukraine will not recognise Russia's annexation of Crimea, saying: "There's nothing to talk about here. This is against our constitution."
Trump, in an online post before the end of the talks in the UK, called this an inflammatory statement that made a peace deal harder to achieve.
The US president said Crimea was lost years ago "and is not even a point of discussion".
"Nobody is asking Zelenskiy to recognise Crimea as Russian Territory but, if he wants Crimea, why didn't they fight for it eleven years ago when it was handed over to Russia without a shot being fired?" Trump wrote on Truth Social.
Russian fighters seized control of the Crimean peninsula in 2014 in a move that was condemned internationally.
Few countries recognise Russia's claim to Crimea.
Trump scolded the Ukrainian leader and said the US was trying to stop the killing in his country and that they were "very close to a deal" for peace.
US Vice President JD Vance said the negotiations on Wednesday were reaching a moment of truth.
"We've issued a very explicit proposal to both the Russians and the Ukrainians, and it's time for them to either say 'yes' or for the United States to walk away from this process," Vance told reporters during a visit to India.
White House spokeswoman Karoline Leavitt said on Wednesday that the US president was running out of patience with the pace of the talks to end the war.
"The president's frustrated. His patience is running very thin. He wants to do what's right for the world. He wants to see peace. He wants to see the killing stop but you need both sides of the war willing to do that," Leavitt told reporters at the White House.
"And unfortunately, President Zelenskiy seems to moving in the wrong direction."
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