NOVELTY - A heterogeneous catalyst system (S1) comprises mixture of amorphous zinc oxide and zinc oxide nanocrystals; and second metal oxide. The zinc nanocrystals have mean grain size of 20-80 nm with at least one of nanocrystals including mesopore having diameter of 5-15 nm. The combination of zinc oxide mixture and second metal oxide has first surface site and second surface site. The first surface site is capable of catalyzing transesterification reaction of triglyceride with alcohol. The second surface site is capable of catalyzing esterification reaction of fatty acid with an alcohol.    USE - Heterogeneous catalyst system (S1) for preparing product, particularly a biodiesel product (claimed).    ADVANTAGE - The catalyst system (S1) has high activity and long lifetime. The alcoholic ester of free fatty acids has greater than about 90% yield.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a product, particularly a biodiesel product, formed by reacting oil with alcohol in the presence of the catalyst system (S1);    (2) preparing the catalyst system which comprises combining zinc salt and second metal salt to form a first aqueous solution; mixing first aqueous solution with aqueous urea solution to form mixed solution; agitating and heating mixed solution until solid precipitate forms in mixed solution; stopping agitation of mixed solution; continuing to heat mixed solution until solution becomes a firm solid; drying firm solid at temperature greater than 100 degrees C for greater than or equal to 1 hour; and calcining solid at elevated temperature for predetermined length of time to obtain desired catalyst system (S1); and    (3) method of forming a product by catalysis which comprises providing the catalyst system (S1); placing feedstock and alcohol in contact with catalyst system (S1) to form reaction mixture, where feedstock includes triglycerides, free fatty acids (greater than 0.5 wt.%), and water (greater than 1 wt.%); heating reaction mixture and allowing catalyzed transesterification of triglycerides and catalyzed esterification of free fatty acids to simultaneously occur to form respective corresponding alcoholic esters of triglycerides and free fatty acids.