WO3 nanoparticles single doped with Ti (W1-xTixO3) and co-doped with Ti and Zn (W1-xTix-yZnyO3) have been prepared, onto FTO/glass substrate. Preparation of films was done using wet chemical method (dipping in a sol-gel). The molar concentration of Ti into W1-xTixO3 ranges from 0-30 % in steps of 5%. Best electrochemical and electrochromic properties were observed for composition that has Ti nominal concentration of 5 % (W0.95Ti0.05O3). This was evidenced from measurements of cyclic voltammetry (CV), chronoamperometry (CA), and transparency during CA. The composition that gives best electrochemical and electrochromic properties (W0.95Ti0.05O3) was used to prepare WO3 nanocrystallite films co-doped with Zn for the first time (W0.95Ti0.05yZnyO3). The Zn molar concentration in these films varied from 1-5%. From CV, CA, and transparency measurements, the best electrochemical and electrochromic properties were observed for films that contains 3% of Zn (W0.95Ti0.02Zn0.03O3). Moreover, this film was found to have better electrochemical and electrochromic properties than single doped WO3 film (W0.95Ti0.05O3). In addition, higher electrochemical stability was observed for co-doped films.