“To do two things at once is to do neither.”
Misattributed as Maxim 7, p. 13 https://books.google.com/books?id=GKFGAQAAMAAJ&pg=PA13&dq=%22To+do+two+things+at+once+is+to+do+neither.%22
Variant of:
Duos qui sequitur lepores neutrum capit
Who chases two rabbits catches neither.
A Dictionary of Quotations in most frequent Use, David Evans Macdonnel, 1797, quoted in The Monthly Review, 1798, p. 467 https://books.google.com/books?id=KYhPAAAAYAAJ&pg=PA467&dq=%22duos+qui+sequitur+lepores+neutrum+capit%22
Apparently of medieval or modern origin, not found in antiquity.
Misattributed