zero crossing detector and reset counter circuit

hi
ok , i am very bad at this circuitry stuff and for my last year project i need to make a counter which count the time differences electric leakage frequency and applied voltage frequency .

the idea is to count the time difference between when a zero cross happens for electric leakage frequency and for a zero cross for applied voltage frequency

anyone knows any diagram for a counter circuit which has a reset function in it. which can be made without buying more stuff .
is there anyone could tell me and give me the schematic for a compilator i could use? or even a zero cross detector

any help is appreciated,even a link would do .

help me obiwan kenobi , your my only hope

dark conqueror