Miroslav Djukic's side looked doomed to be relegated back to La Segunda before the Serbian took over from Albert Ferrer in October, but they have since climbed out of the bottom three and Friday's midfield reinforcements strengthen their chances of avoiding the drop.
Zuculini's loan at Valencia was cut short earlier in the day by parent club Manchester City, while Krhin – co-owned by Bologna and Inter – and Sporting Lisbon's Heldon also joined on temporary deals.
Zuculini was not the only Man City player to end up in La Liga, as Nigerian youngster Chidi Nwakali agreed a two-and-a-half-year loan deal with Malaga.
Levante also had a successful day, as experienced centre-back Ivan Ramis arrived from Wigan Athletic and the league ratified Kalu Uche's free transfer.
Following Ramis back to Spain from England are Adrian Colunga and Rafa Paez.
Forward Colunga joined goal-shy Granada on loan from Brighton and Hove Albion, while Liverpool's 20-year-old centre-back Paez links up with Eibar.
Also heading to Granada until the end of the season is Jose Manuel Casado, leaving Malaga after making just two Liga appearances since joining from Rayo Vallecano in September 2013.
Few of the division's bigger sides were active on deadline day, although Villarreal's move for Espanyol's Eric Bailly went through, Real Sociedad completed the signing of Nabil Bahoui from AIK and Sevilla allowed Bryan Rabello to join Leganes until June.
