You need to make sure that the two fixtures added together are somewhat lower than the switch rating. When you remove the tab on the line side of this switch it will now handle two completely separate and isolated switching functions.
Switches Ultimate Electronics Book
Combine two light switches into one. Neutral is in a pigtail without connecting to any switch. Obviously without any sort of specific specifcations i cannot give you a part number that will help you out. They are connected to their own loadlineground wires. Those two light switches are in the same switch box and the same circuit. If not your gonna need a bigger switch. Now just pass the two switch legs through this switch.
However if you do not wish to splice the two wires together there is an alternative. Electrical lighting i have a 3 gang box and im interested in combining 2 of the existing single pole light switches in the box into 1 switch that controls. Now with one single device you can switch two items. Dont change anything on the neutrals whites and all the grounds should all go together. All you need to do is hook one of the hot lines to the switch and cap the other hot line with a wirenut. Leviton as well as many other companies make a switch that has two single pole switches built into one switch.
Combining 2 switches into 1. Then pigtail both of the two switched lines that return to the fixtures to the switch output side.