After doing some research I found one important celebration, and that is Independence Day. Zimbabwe first Celebratied independence day in 1980 and ever since it has been quite an important cellebration. There may be more information on Zimbabwe's Wikipedia page, but Independence day is the only celebration mentioned on it. I also inquired further into more of their celebrations and and there is an Africa Day- which commemorates the struggles of African Independence. There is Heroes Day, Zimbabwean Music Festival, Zimbabwe International Trade Fair, New Year, Independence Day and Christmas.
The 3 Main Celebrations would seem to be
and Heroes day
Also the 2 other important Celebrations would be
and New Year
To conclude these events in importance order are: Independence Day, Africa Day, Heroes Day, Christmas, New Year, Zimbawean International Trade fair and then Zimbabwean Music Festival