And in a poll, Mr Musk asked Twitter users to vote on if “the will of the people who live in the Donbas and Crimea should decide whether they’re part of Russia or Ukraine”.
In another post, the billionaire called for the sham referendums conducted by Moscow to be redone under the supervision of the UN. He also said Crimea should be under Russian control.
The survey from Mr Musk was created days after the US, G7 and western nations condemned President Vladimir Putin for announcing Russia had annexed the Ukrainian regions of Luhansk, Donetsk, Zaporizhzhia and Kherson.
Mr Zelenskyy responded with his own poll, asking users: “Which Elon Musk do you like more?” with the options listed as: “One who supports Ukraine” and “One who supports Russia”.
Mykhailo Podolyak, adviser to the Ukrainian president's chief of staff, replied to Mr Musk, saying there “is a better proposal” that includes the liberation of the territories — including Crimea — from Russia.
The proposal also includes de-militarisation and de-nuclearisation of Russia, and that “war criminals go through international tribunal”.
"Tesla is a nice car for sure. But today I prefer Himars,” Mr Podolyak later tweeted, referring to the rocket systems provided by the US.
Andrij Melynk, Ukraine's ambassador, gave a harsh “diplomatic response” to Mr Musk on Twitter.