First up is "The Zen Diaries of Garry Shandling," a two-part, four-hour-plus deep dive (and then some) from writer-producer-director Judd Apatow, who cut his professional teeth working for Shandling on "The Larry Sanders Show." A week later, the network will air "Arthur Miller: Writer," an extraordinary look at the playwright by his daughter, Rebecca Miller, culled from years of footage, including late-in-life interviews with her dad.The filmmakers don't hide their personal connections, but these aren't necessarily unvarnished paeans of praise. Apatow, in particular, captures Shandling's insecurities, impatience and mercurial nature, which included frustration when collaborators didn't match his perfectionism, prompting even friend Kevin Nealon to call him "a handful."Perhaps the most fascinating aspect of "Zen Diaries" can be found in that title, as the project draws extensively on Shandling's private diaries, where he does everything from dissect the art of comedy ("commit to killing; commit to the performance") to vent about his anger toward his manager Brad Grey ("He betrayed my trust … I hate him"), who Shandling wound up suing for millions in one of the more acrimonious professional divorces that Hollywood has ever witnessed.Related: Garry Shandling shares his thoughts on Johnny CarsonIf there's a Rosebud in this "Citizen Kane"-like deconstruction, it can be found in the death of Shandling's older brother when he was just a kid; and a certain paranoia that actually turned out to be well founded, given that he wound up having his phones tapped by private investigator Anthony Pellicano.Like a lot of famous comics, Shandling's zen-like qualities didn't include always enjoying his success. His career was characterized by a restlessness, despite conquering standup and then TV with "It's Garry Shandling's Show" and "The Larry Sanders Show." Unlike contemporaries Jay Leno and David Letterman, Conan O'Brien notes that Shandling was one of those people who "can't crank it out for all of eternity."Despite identifying Shandling as his mentor, even Apatow concedes, "In a lot of ways, he was a mystery to me." "The Zen Diaries" don't completely decipher the riddle that was Garry Shandling, but nevertheless offers a fascinating window into one of comedy's most fertile minds.Perhaps inevitably, "Arthur Miller: Writer" isn't as fully realized, but it's difficult to top the access that his daughter enjoyed, with a project that she filmed over the course of 20 years, complete with everything from casual chats to watching her dad therapeutically tinker away in his workshop.A bit slow in the early chapters devoted to Miller's family history, the documentary takes off once the playwright's career kicks into gear, with plays like "Death of a Salesman" and "The Crucible."There are also the matters of Miller's relationship with director Elia Kazan, how that was impacted when both were called before the House Un-American Activities Committee, and naturally, Miller's marriage to Marilyn Monroe, which turned him into a supporting player, at least in the public's eye, in the actress' chaotic life.The film contains other sobering personal material, from Miller's approach to fatherhood ("I just couldn't be a father 24 hours a day and still do what I had to do") to the pain of giving up a child diagnosed with Down Syndrome at birth.Weaving in interviews with other stage titans like Mike Nichols and Tony Kushner, Rebecca Miller captures her father's enormous influence, as well as the shifting perceptions of it as America moved through the tumult of the 1960s.Still, it's Miller who gets the last word, when Charlie Rose asks what he would like his obituary to say. "Writer," Miller responds, exhibiting a gift for, among other things, understatement."The Zen Diaries of Garry Shandling" will air March 26-27 and "Arthur Miller: Writer" on April 2, all at 8 p.m. on HBO.