EastEnders star Michelle Ryan is to leave the BBC soap over a year after making her return as Zoe Slater.The 42-year-old returned to Albert Square last summer as she reprised her role for the first time in 20 years.Zoe has been at the centre of the drama since she has been back, having spent months searching for her twin son and daughter – Josh and Jasmine – who she had secretly given birth to.She also spent weeks wrongfully imprisoned after being accused of the murder of her ex-boyfriend Anthony Trueman.