Workability is the ability that you have and can apply in your work ( job). This is more or less like the knowlodge of work in group/teams and you apply it in your work, or what you learn in your university course or in another kind of course,
Employability is defined like "doing value creating work, gettong paid for it - and learning at the same time". This can help to get a work in future. Maybe this involve your personal abilities and knowlodge about yourself, and about your job area. Making you "flexible" in time to get a work or in job market. An example is you have a lot of kinds experiences that makes you can get a lot of kinds of jobs, It is very good in bad times like now, the person who have this skill have good chances to get a job and never be in a bad situation like unemployed.