I can do all things (panta iscuw). Old verb to have strength (iscu). In him that strengtheneth me (en twi endunamounti me). Late and rare verb (in LXX) from adjective endunamo (en, dunami). Causative verb to empower, to pour power into one. See same phrase in 1 Timothy 1:12twi endunamwsanti me (aorist tense here). Paul has such strength so long as Jesus keeps on putting power (dunami) into him.