The main difference between a zinc battery and an alkaline battery is the type of electrolyte used in both batteries. Because of the composition, an alkaline battery delivers more energy than a zinc battery. Both batteries should thus be used in different appliances.
Zinc air battery are different from other batteries. They do not contain active materials in their positive electrode. This type of battery reacts with air - so it’s important to remove the tag before inserting the battery into your device. They provide a current of 1.4V if used correctly.
The results of a voltmeter vary depending on the type of voltmeter used. For a more accurate result, be sure to use a voltmeter with more than 1 megaohm input resistance for alkaline buttons batteries or a 10+ megaohm for lithium batteries.