The 27-year-old, who joined the Hammers in the summer from Velez Sarsfield, has started just five games, and is set for the exit after a stunning bust-up with manager Sam Allardyce.
Zarate, who reportedly completed a medical with QPR last week, launched a stinging attack on manager Allardyce, saying that 'Big Sam' had been disrespectful for not playing him in the first team more often.
Allardyce responded just a day later, saying that the Argentine-turned-Chilean simply wasn't good enough to get in the Hammers starting XI ahead of the likes of Andy Carroll, Diafra Sakho and Enner Valencia.
A deal with QPR seemed like a formality, but speaking after QPR's 1-1 draw with Swansea City on New Year's Day, manager Harry Redknapp wasn't quite so confident.
"I’m not sure," he said. "We’ll wait and see what happens. We’ll have to look at it and see where we go."
Redknapp was then asked on whether he thought Zarate would eventually join the R's, and he again responded with; "Maybe. I’m not sure."
It's strange for Redknapp to be so unsure on the move just days after reports suggested that Zarate had completed a medical and would sign a six-month loan deal at Loftus Road - and maybe the war of words with Allardyce has put him off.
That could work two-fold; Zarate's petulant attitude to being left out of the side could be a huge concern for Redknapp, whilst Allardyce's claims that Zarate just wasn't good enough will also set alarm bells ringing for Redknapp.
This is a situation to monitor, but make no mistake - Zarate won't be at Upton Park for long given his public spat with his own manager Allardyce, and whether it's QPR or another team, he'll be heading out of East London this month.