You don't need any apps to work with the website version of Zotero on your mobile device - simply go to your Zotero website via your mobile browser and choose the Web Library tab.

From here you can also create simple bibliographies. First hold the control (or command key on a Mac) to select the sources for your bibliography. Then choose the create bibliography icon from the menu.

Then choose the citation style you would like to use. Notice that you can add citations from Zotero's full citation library. Then copy your bibliography to the clipboard and paste the bibliography wherever you would like to use it.