[4] Zimmer's stage career was highlighted with her award-winning portrayal in a Los Angeles production of Catholic School Girls, where she won a Dramalogue for Best Actress.

[4] After starring in several national commercials,[4] most notably for Duracell, she started making guest appearances in such shows as Ellen, Seinfeld, The X-Files, Gideon's Crossing, and The King of Queens,[4] as well as having recurring roles in The Wayans Bros., Hyperion Bay, and The Trouble With Normal.

[4] Zimmer eventually booked her first TV series regular role on the NBC comedy Good Morning, Miami as the lazy and burned-out office assistant, Penny Barrington.

After the series was canceled, she spent the second season recurring as Sister Lilly Waters in the CBS drama, Joan of Arcadia, as well as guest-starring in episodes of NYPD Blue and Jake in Progress.

[5] Zimmer also portrayed industry powerhouse and studio executive Dana Gordon in the HBO original series Entourage from 2005 to 2011, arguably her most known role to date.

Zimmer performed in the world-premiere play, Girls Talk, alongside Brooke Shields, Andrea Bendewald, and Nicole Paggi.

She also starred in the NBC summer series Love Bites as Colleen Rouscher and had a guest appearance on USA's Royal Pains, playing psychiatrist Dr. Abby Burton.