I recently ordered PICProto-18, PICProto-Dual, and PICProto-64
    from Micro Engineering. I was disappointed that the board layout
    of all three does not lend itself to installing ZIF sockets. I'm
    currently using Aries 28 and 40 pin sockets and AMP (Textool) 18 pin.


You could try the multi-socket hack used for debugging large chips (I
think this was invented for dealing with the 68000 64-pin .9inch DIP.)
You pile up sockets in each other until it's high enough off the board
to attach the ZIF socket.  It could also be done with WW socket:

        *BIG BAD**
        **ZIFSOCK*
           |  |
        C  WWSK
         O |  | R
        MP |  | R
   -------Board----

BillW