I forgot that this was Civ 2 and not Civ 3 where you lose shields for changing options so on all my polls pretend it says build another pikeman rather than finish the pikeman...So these polls are now for the next build option and all the cities will have to finish building their Pikeman.
I should have voted for other and then specified a diplomat. With some commerce behind it, it can be a better defender than just about anything, and it does not cost a shield to support. In fact, I would even suggest changing the pikemen over to a dip if there's still time. The backwards zulus will take ages to produce any powerful mounted units like crusaders.
Don't forget, you can change from one military unit to another with no penalty in Civ2 - just as you can change from one improvement to another (or from wonder to wonder). The penalty only takes shape when you go from improvement to military or vice-versa (or from or to a wonder).
I ended up, however, voting for crusaders. It may not be a horrible idea still to change to crusaders. If pikemen are already finished, then I'd go with a diplomat.
EDIT: As a bit of micromanagement might I suggest moving a worker off of a grassland tile and put it on the irrigated and roaded plains? It would still produce two food and one shield, but the road would at least give a bit of commerce.