Zip Co Ltd (ASX: ZIP) shares just finished off one heck of a month.

Shares in the S&P/ASX 200 Index (ASX: XJO) buy now, pay later (BNPL) stock plunged 34.6% in March, closing out the month trading for $1.61 apiece.

Amid concerns that United States President Donald Trump's tariffs could impact Zip's primary consumer markets of the US, Australia, and New Zealand, and potentially lead to higher interest rates, the selling action continued into early April.

On 7 April, Zip stock closed down 7.4% at $1.19 a share.

But things took a huge turn for the better from there.

With investor sentiment swinging into the bull camp, Zip shares ended April trading for $1.73 each. This saw the ASX 200 BNPL stock up 7.5%. That's more than twice the 3.6% gains posted by the ASX 200 over the month.

It also put Zip stock up a remarkable 45.4% from the 7 April close.

Here's what really helped turn the tide.

How Zip shares pasted the ASX 200 in April

Zip shares enjoyed their first big boost on 8 April.

That's when management announced their plan to undertake an on-market share buyback of up to $50 million. When a company buys back its shares, it reduces the supply of those shares available to investors, which tends to support the share price.

"The buy-back program we have announced today is consistent with our capital management framework and focuses on maximising shareholder returns," Zip CEO Cynthia Scott said on the day.

Also likely helping to boost investor sentiment, Scott added, "Zip will maintain a strong balance sheet following completion of the buy-back with ongoing flexibility to pursue future growth opportunities."

What else boosted the ASX 200 BNPL stock in April?

The second big tailwind for Zip shares came on 16 April, when the company announced its third-quarter results.

Investors sent shares to close up 16.2% on the day after the company reported a 36% year-on-year increase in quarterly total transaction value (TTV) of $3.3 billion.

Total income of $279 million was up 27%, while cash earnings before tax, depreciation and amortisation (EBTDA) surged 219% from the prior corresponding quarter to $46 million.

With that strong quarter in the bag, Zip upgraded its full year FY 2025 guidance, with management expecting to deliver cash EBTDA of at least $153 million. That was up from Zip's prior earnings guidance of at least $147 million.

And Zip shares are enjoying a strong start to the new month.

In late morning trade today, shares are up 0.6% at $1.74 each.