Pin Damaged question

thank you for your answers..

the I/O standard is 3.3LVTTL or 3.3LVCMOS.

and the application is writing and reading data to and from this connectors..

the IO pins are already connected to Pullup resistances outside the FPGA and the IO pins are open drain.. and the supply voltage is 3.3V.

but I do not understand something..

the function of the zener diode is to limit the voltage to 3.3V(VP), is n't it?

so any voltage above this value will be clipped to this value(3.3)..

is that true?

and the diodes are to eliminate the effect of the ESD(electrostatic discharge)..

will it work with this value(3.3V) ?