Illustration has always been an integral part of Jonathan's life. Born in 1992 in Colombia his first memories are of early mornings sitting on the floor drawing mermaids and all sorts of sea creatures on the  living room's coffee table while cartoons played on the TV. This early influence carried to his life coming to the United States at 13 and later graduating high school to study marine biology, putting art aside as a back up. It wasn't until the end of his college freshman year that he realized marine biology was not what he really wanted to do.

After this he took three years off school to find what his true calling was, which he spent working in tattoo shops as manager and ultimately as a tattoo apprentice. It was during this three-year gap that Jonathan discovered he just wanted to illustrate for a living, regardless of the medium. Returning to school he obtained his BFA in Illustration and started working digitally after having worked traditionally for his entire life. Jonathan, now going by J. Z. Castillo, began illustrating his comic book Rise of Omega as his first, long-running project, something he has been writing since 2008 and has just recently started to illustrate between other projects and commissions.

His style is influenced by western animation and eastern comics, using heavy linework, soft and hard shading between colors, borrowing from life and graphic aesthetics. The illustrations carve an uncanny valley, where the subjects look human and believable but are also recognized as a verisimilitude of life, alluding to what is real.