Yes. You can share the sensors without further configuration.
For actuators the easiest approach would be to physically swap the connector. For example: use two slots on the bottom for fermentation, and two on the top for HERMS.
It’s also possible to do it in software using the Logic Actuator (https://brewblox.netlify.app/user/all_blocks.html#logic-actuator). Before running the quickstart wizards, create a Mock Pins block, and use that as target in the wizards. Don’t overwrite pins in the second wizard.
Afterwards, create a Logic Actuator and a Digital Actuator for each SSR. The two actuators you want to share an SSR are input for the logic actuator, and the created Digital Actuator is output. Use an
a^b expression to be safe. The inactive chain must always be disabled to prevent it trying to control the output.