With Russian forces gaining momentum on the front and aid from allies ebbing or in doubt, Zelensky has launched an ambitious diplomatic offensive to end the war grinding through its third year.
He gathered leaders and top officials from dozens of countries at the Swiss mountainside resort of Burgenstock in June for a first summit, which Russia derided as a waste of time and China shunned.
While the Kremlin was not invited to the first gathering, now is the time for Moscow to take a seat at the table, Zelensky said.
"The majority of the world today says that Russia must be represented at the second summit, otherwise we will not achieve meaningful results," he said in western Ukraine on Tuesday.
"Since the whole world wants them to be at the table, we cannot be against it."
Russian President Vladimir Putin has said he is open to negotiations, but would only order a ceasefire if Kyiv effectively surrendered territory that Moscow claims as its own.
Zelensky's push focuses on a sweeping 10-point plan that would restore Ukrainian territorial integrity, return prisoners of war and give Ukraine energy and economic guarantees.
He acknowledged that China was a key player but said he did not want mediation from Beijing and instead urged it to pressure the Kremlin to end its invasion.
"If China wants, it can force Russia to stop this war," Zelensky said.
While the Ukrainian leader has won broad international backing for his peace efforts, Zelensky hit out at some of those same allies for barring his army from using their weapons to hit deep inside Russian territory.
"It's a serious challenge that we can't use all the weapons we need to stop this enemy. What would you do if you were us?" he said.
He also criticised stilted arms deliveries, saying Ukraine was still waiting for weapons from allies to equip recently mobilised troops.
And if Ukraine breaks the terms of use for Western-donated weapons "then they can say that we won't give you any more help -- that's the risk", he said.
Zelensky met with French media at a school gym in the western town of Rivne, after being whisked from a gathering to hear grievances of local businesses and a meeting with local officials.
Only one day earlier he had handed out awards to special forces in the frontline Kharkiv region more than 800 kilometres (500 miles) away.
Despite his wall-to-wall itinerary that this year has included visits to Asian and European capitals, one trip he has not made was to the opening ceremony of the Olympic Games in Paris.
"I would have loved to attend if this wasn't such a difficult time in my country. It is a tense moment in the east of our country," he said, referring to Russia's capture of a slew of villages in the industrial Donbas region.
Zelensky criticised the International Olympic Committee's decision to allow some Russian athletes to compete at the Paris Games under a neutral flag.
"Let there be bloodstains on it, and then let them compete," he said, calling the IOC decision "piecemeal sanctions".
With uncertainty for Ukrainian forces looming over the sprawling eastern front line, Zelensky also conceded that a neck-and-neck presidential race in the United States -- a vital political and military ally -- presented further "risks".
Washington has provided tens of billions of dollars in military assistance for Kyiv since Russia launched its full-scale invasion of Ukraine in February 2022.
But a victory for Republican candidate Donald Trump -- who claims he will be able to force the sides into a negotiated settlement -- would bring Washington's continued support into question.
"We cannot influence any election," he told reporters. "Of course, the United States is a challenge today. And there are risks that probably none of us can predict."
The Democrats' presumptive White House candidate Kamala Harris has echoed President Joe Biden's pro-Ukraine stance.
Zelensky said his team had been in touch both with her aides and the Trump campaign.
"As president of Ukraine, I must, of course, have a dialogue between my team and the Biden, Trump, and today Harris teams," Zelensky said.
"We have to have all these contacts and talk about what our future might look like if one side or the other wins the election."