Is it safe to switch from fosinopril 20mg to lisinopril 20mg?

Generally, yes: Lisinopril and fosinopril are generally swappable mg for mg, and as members of the same drug class, are generally equally well tolerated.

Ace inhibitors: Same class of medications. Dosage equivalent. Only concern would be if you had a problem with fosinopril. Common side effects cough, facial swelling can have adverse effect on kidneys and potassium in rare individual.