Zelenskiy made his first public acknowledgement of the operations on Wednesday in remarks to reporters that were embargoed until Friday.
He said Ukrainian forces took part in active operations abroad using domestically produced interceptor drones proven in countering Iranian-designed Shahed drones used by Russia in Ukraine.
"This was not about a training mission or exercises, but about support in building a modern air defence system that can actually work," Zelenskiy said.
Ukraine took part in the defensive operations before the tentative ceasefire in the Middle East was reached among Iran, the United States and Israel this week.
Zelenskiy did not identify the countries involved but said Ukrainian personnel operated across several nations, helping strengthen their air defence systems.
In exchange, Ukraine was receiving weapons to protect its energy infrastructure, along with oil, diesel and, in some cases, financial arrangements, he said.
The Ukrainian leader said the agreements would bolster Ukraine's energy stability and described the partnerships as something that would "be marketed" as Kyiv seeks to formalise and expand its defence export role.
"We are helping strengthen their security in exchange for contributions to our country's resilience," he said.
The disclosure comes amid concerns that conflict in the Middle East could divert Western military support from Ukraine, particularly air defence supplies.
But Zelenskiy said that partners were continuing to supply missiles for Patriot systems, adding that a new batch had arrived in recent days and that Ukraine was working with all partners to ensure its air defence remained in place.
He warned that the coming spring and summer would be difficult for Ukraine, with growing political and battlefield pressure as the United States turns to domestic politics and elections.
Zelenskiy said he had urged US envoys Steve Witkoff and Jared Kushner to visit Kyiv and proposed a trilateral format with Moscow.
US-led talks have made no progress on key issues, as Washington's attention shifts to the Middle East conflict while Russian and Ukrainian forces remain locked in fighting along the 1200km front line.
Separately, Zelenskiy said he expected Western allies to restore full sanctions on Russian oil, warning that any easing could allow Moscow to sustain its war effort.
Russia has been profiting from a surge in global energy prices, brought on by damage to oil and gas infrastructure in the Gulf and Iran's blocking of the Strait of Hormuz, a vital sea route for global oil supplies.
Ukraine has stepped up strikes on Russian energy sites to cut oil revenues as prices rose and US sanctions eased.
Zelenskiy said partners had urged Kyiv to scale back attacks during Iran's disruption of the Strait of Hormuz, but he argued Russian oil had a limited impact on global markets.
Zelenskiy said Ukraine was ready to mirror any ceasefire steps after Russian President Vladimir Putin announced a temporary Easter truce.
"We proposed a ceasefire during the Easter holidays this year and will act accordingly", Zelenskiy said on Friday on X.
"People need an Easter free from threats and real movement toward peace, and Russia has a chance not to return to strikes after Easter as well."
Putin on Thursday declared a 32-hour ceasefire over the Orthodox Easter weekend, halting Russian hostilities from Saturday afternoon until the end of Sunday.
Previous ceasefire attempts have had little impact, with both sides accusing each other of violations.
