While Zohran Mamdani won the NYC Democratic mayoral primary and the Board of Elections released ranked-choice voting results, there is no clear evidence in the sources that his campaign earned the most votes in a primary in NYC history.
Board of election in NYC released RCV totals and states Zohran Mamdani campaign earned the most votes in a primary in NYC history.

FactVerify
Source: factverify.com
What the Evidence Shows
The claim states that the NYC Board of Elections released ranked-choice voting (RCV) totals and that Zohran Mamdani's campaign earned the most votes in a primary in NYC history. The search results confirm that Mamdani won the Democratic mayoral primary in New York City and that the Board of Elections released RCV results.theguardian.comtheguardian.comZohran Mamdani declares historic victory in New York City mayoral primary after...
nbcnewyork.comnbcnewyork.comNYC primary results: Ranked choice voting update released today
nytimes.comnytimes.com‘We Have Won,’ Mamdani Says, as Cuomo Concedes N.Y.C. Mayoral Primary Mamdani's victory was described as historic and notable, with Cuomo conceding and acknowledging Mamdani's strong campaign.
theguardian.comtheguardian.comZohran Mamdani declares historic victory in New York City mayoral primary after...
foxnews.comfoxnews.comModerate rivals plot to block Mamdani's NYC election bid after primary victory
nytimes.comnytimes.com‘We Have Won,’ Mamdani Says, as Cuomo Concedes N.Y.C. Mayoral Primary
However, none of the provided sources explicitly state or verify that Mamdani's campaign earned the highest number of votes ever recorded in a NYC primary. The sources focus on his victory and vote percentages but do not provide historical vote totals or comparisons to previous primaries. Without explicit data or statements from the Board of Elections or credible news reports confirming this specific record, the claim cannot be fully verified based on the available information.