I really wish this what what Corbyn actually did, since I believe that the key to moving that conflict towards a peaceful resolution is the promotion of mutual understanding and recognition of the conflicting narratives adhered to by each side.
That's not what Corbyn and the section of the left he's been involved with his entire career does though. Instead, they offer solidarity and legitimacy to all expressions of the Palestinian narrative, while completely denying and rejecting the Zionist narrative. So their 'criticism' of Israel goes beyond any specific Israeli policies or actions and portrays Zionism as inherently racist, colonialist, etc., basically illegitimate and beyond-the-pale (which is why Nazi analogies, which no serious person could consider legitimate, come so easily to them).
This refusal to consider the range of historical and contemporary factors which have made and continue to make Zionism appeal to so many Jews ultimately produces car crash interpretations of the 'Zionist endeavour' such as
this; and it immediately signals to the vast majority of Jews in Israel (not to mention elsewhere) that there is no space for their narrative in your idea of a 'peaceful' Palestine, and that the key to achieving that peace is their defeat.
And, unless Corbyn is pulling them aside to tell them that empathy, negotiations, and non-violence are the way forward (does anybody actually believe this to be the case?), it encourages his Palestinian interlocutors in the belief that 'victory' (i.e. the defeat of Zionism) and not compromise is the only just path to peace.
Now you could argue that what Corbyn is doing is providing a counter-balance to a mainstream discourse in which it is the Palestinian narrative that is under-represented. But assuming this is true, it's (a) not what he claims to be doing, and (b) unclear how this helps the path to a negotiated peace, since it completely alienates one of the parties to the conflict.
Ultimately, despite all his platitudes, the brand of anti-Zionism which Corbyn and his associates adhere to is a hindrance to the pursuit of real peace over there. If he was honest, he'd just admit that it's a Palestinian victory he's interested in.