Context : Oxygen and zinc in the Galactic bulge are key elements for the understanding of the bulge chemical evolution .
Oxygen-to-iron abundance ratios provide a most robust indicator of the star formation rate and chemical evolution of the bulge .
Zinc is enhanced in metal-poor stars , behaving as an \alpha -element , and its production may require nucleosynthesis in hypernovae .
Most of the neutral gas at high redshift is in damped Lyman-alpha systems ( DLAs ) , where Zn is also observed to behave as an \alpha -element .

Aims : The aim of this work is the derivation of the \alpha -element oxygen , together with nitrogen , and the iron-peak element zinc abundances in 417 bulge giants , from moderate resolution ( R \sim 22,000 ) FLAMES-GIRAFFE spectra .
For stars in common with a set of UVES spectra with higher resolution ( R \sim 45,000 ) , the data are intercompared .
The results are compared with literature data and chemodynamical models .

Methods : We studied the spectra obtained for a large sample of red giant stars , chosen to be one magnitude above the horizontal branch , using FLAMES-GIRAFFE on the Very Large Telescope .
We computed the O abundances using the forbidden [ OI ] 6300.3 Å and Zn abundances using the Zn I 6362.34 Å lines .
Stellar parameters for these stars were established in a previous work from our group .

Results : We present oxygen abundances for 358 stars , nitrogen abundances for 403 stars and zinc abundances were derived for 333 stars .
Having oxygen abundances for this large sample adds information in particular at the moderate metallicities of -1.6 < [ Fe/H ] < -0.8 .
Zn behaves as an \alpha -element , very similarly to O , Si , and Ca .
It shows the same trend as a function of metallicity as the \alpha -elements , i.e. , a turnover around [ Fe/H ] \sim -0.6 , and then decreasing with increasing metallicity .
The results are compared with chemodynamical evolution models of O and Zn enrichment for a classical bulge .
DLAs also show an enhanced zinc-to-iron ratio , suggesting they may be enriched by hypernovae .

Conclusions :