After returning to Dinamo Zagreb in 2013, Zelenika moved to Lokomotiva in 2014 on a loan spell lasting until the end of the 2015–16 Prva HNL season.

On 23 July 2013, after an abrupt departure of the club's first-team goalkeeper Pablo Migliore, Zelenika was fielded by the head coach Krunoslav Jurčić in a 2013–14 UEFA Champions League qualifying phase home match against Fola Esch, thus making his first official appearance for the club and also keeping a clean sheet in a 1–0 win.

[4] He would make his first league appearance for the club five days later, playing a full match and keeping a clean sheet in a goalless draw against Rijeka.

[6] A backup for Dušan Kuciak, he went on to feature in a single league match - a goalless home draw with Cracovia on 23 April 2018.

Zelenika signed a contract until the end of the season with the option of an additional year for the Dutch Eerste Divisie side NEC Nijmegen on 29 October 2018, following the injury of the first-choice keeper Norbert Alblas.

With regard to his goalkeeping skills, football coach Krunoslav Jurčić described Zelenika as an ideal player for the teams with a strong defensive play that will make the goalkeeper behind it idle for most of the match and then require of him to keep his focus high when reacting to those handful of shots that the opposing team may direct at the goal.