Actress Madeline Zima Hopes Hayden Panettiere's Daughter Knows How Great She Was

Madeline Zima -- one of Hayden Panettiere's co-stars on the hit show "Heroes" back in the day -- says the actress was incredibly kind ... and she's speaking out in hopes Hayden's daughter will one day know how great her mom was.

We sat down with Madeline on our "TMZ In The Know" YouTube series ... and she told us she remembers Hayden as someone who was all heart and guts.

Madeline notes she's been in the film and TV world for a long time -- starring in "The Nanny" when she was just 8 years old -- and she calls Hayden one of the kindest and most loving people she's met in the industry.

She tells us Hayden always wanted to do what was best for everyone else ... even if that meant keeping her distance from them.

Ultimately, Madeline says she's speaking out in hopes Hayden's daughter, Kaya, will one day get to know her mom through the love and stories of others.

Madeline and Hayden famously shared a steamy scene in Season 4 of "Heroes" ... when they shared a daring kiss.

Hayden was a main cast member on the show, appearing in 75 of its 77 episodes ... more than any other actor. Madeline was credited for 10 episodes in the show's final season.

While still working on "Heroes," Hayden met boxer Wladimir Klitschko. The two began a 9-year relationship in 2009 -- and she gave birth to Kaya in 2014. He gained full custody of Kaya in 2018.

As we reported ... Hayden was found unresponsive Sunday at a South Carolina residence. First responders tried to resuscitate her, but she didn't make it.