Problem installing zoo package

[mara]

This isn't the question you're asking, but you're running a version of R that is quite old, and, based on the error message, it sounds like you're working with someone or some data that is using a newer version (i.e. >= 3.5.0), so you're getting that error on load. See this answer for details:

Error listing packages, Error in readRDS(pfile): cannot read workspace version 3 written by R 3.6.0

What version of R are you running? The default serialization format for R changed in May 2018, such that new default format (version 3) for workspaces saved can no longer be read by versions of R older than 3.5 (you can see relevant commits in the CRAN mirror below) R 3.5 was a major update that required new installations of all packages (see post below) All of which is to say that I would recommend updating your version of R.