In 1962, Dietl changed jobs, moving to the Czechoslovak State Film Agency, eventually becoming a professional writer.
Dietl is known mainly for his work on the television series Hospital at the End of the City, The Youngest of the Hamr Family, Muž na radnici, Plechová kavalérie, Žena za pultem, Okres na severu, Synové a dcery Jakuba skláře, and Frankenstein's Aunt, as well as the films Tři chlapi v chalupě and Nejlepší ženská mého života.
Dietl wrote a number of plays, television series, and film scripts, and also published in the daily Mladá fronta and the magazine Dikobraz.
Dietl is considered to have been the first Czech writer to create multi-generational drama series, usually on a grand scale.
The scheme of his narration was based on certain social environments, such as health, agriculture, industry, and trade, which framed the behaviour and relationships of his characters.