Regarding the zeners, you do not have to worry about that. Programmer takes care of the voltages needed for every chip by its own.

When I said about bias, I meant that you did not left the pin MCLR free in the air (especially if that pin is programmed as a MCLR pin). It should have a resistor of around 10K to the Vdd rail.

Otherwise this could lead to random resets of the PIC.

Ioannis