In Sept. 2015, when we landed in Harare from JNB, we had to fill out the forms at the counter. Forms were not distributed on the flight ahead of time. We tried to get the visas at the Zimbabwean Consulate ahead of time but they ran out of "single-entry" visas and told us just to get the visa upon arrival. You will need to pay with newer USD. Nothing before 2006 if I recall correctly.