on ramp, put scv in front of marines. zealot who targeted ur marine will try to run around the scvs who are blocking the way but wont be able to. by the time the scvs are dead u should have killed some of the units. also 4 marines and 2 meds can kill 5 zeals-put it into a ratio to get ur rush defense fiured. or set a supply depot near entrance to block the zeals way and use marines/hydras to attack from range.if toss use a pylon instead and try to have either goons or cannons for defense.