Re-zoning a property to make a deal work

So I have the opportunity to buy a property in a great city I know well. It is a 1 Acre lot, with 2 homes on the lot. One home is a 2 bed 1 bath, and the other is a 4 bed 2 bath. They both need work, the larger home much more than the the smaller. But with what the property is listed for, the deal doesn't work unless I am able to split the lot into two parcels. It is zoned R40 - So I would need to rezone the property to be able to split the land. Has anyone gone through the process of rezoning, and if so, what are the chances I will successfully be able to get the property rezoned. It would be a great addition to the portfolio if possible, but I don't want to purchase if it's not a strong possibility.