Difference in the total ammonia concentration and the Zinc concentration

For a pH 10 buffer containing ammonia (pKb=4.756) and ammonium at total concentration of 1.0 M, calculate the fraction of Zn2+ in the un-complexed form ([Zn2+]). 
Assume that the Zn concentration is 0.00100 M calculate the pZn2+ at 2, 4, 5, 8, 9.9, 10, 10.5 mL when 100 mL of this zinc solution is titrated with a standardized 0.0100M EDTA solution. (2, 5, 8, 9.9, 10, 10.5 mL). Hint: There is a large difference in the total ammonia concentration and the Zinc concentration so make a sensible approximation
Zn2++NH3‹‡ZnNH32+‹  ,  Î²n1‹=102.21  
Zn2++2NH3‹‡Zn(NH3‹)22+‹  ,  Î²n2‹=104.50  
Zn2++3NH3‹‡Zn(NH3‹)32+‹  ,  Î²n3‹=106,86  
Zn2++4NH3‹‡Zn(NH3‹)42+‹  ,  Î²n4‹=108.88  
Zn2++H2‹O‡ZnOH+  ,  Î²h1‹=10ˆ’8.997  
Zn2++2H2‹O‡Zn(OH)2‹  ,  Î²h2‹=10ˆ’16.894  
Zn2++3H2‹O‡Zn(OH)3ˆ’‹  ,  Î²h3‹=10ˆ’28.391  
Zn2++4H2‹O‡Zn(OH)42ˆ’‹  ,  Î²h4‹=10ˆ’41.118